Track changes in database structure
There are couple of ways to do such forensic analysis :


Using Default trace (provided that the default trace is running). The default trace create 5 *.TRC file that are recycled when they arrive to 20 MB size. :

-- create a test procedure .. so that we can drop it
use test_kin
go
create procedure usp_ABOUT_TO_DELETE 
as
select name from sysobjects
where type = 'U'
order by name 

-- now drop the procedure
drop procedure usp_ABOUT_TO_DELETE




Below is the sql to get details out of the default trace :

         /*
          Object Altered
          Object Created
          Object Deleted 
          */

SELECT TE.NAME
    ,v.subclass_name
    ,DB_NAME(t.DatabaseId) AS DBName
    ,T.NTDomainName
    ,t.NTUserName
    ,t.HostName
    ,t.ApplicationName
    ,t.LoginName
    ,t.Duration
    ,t.StartTime
    ,t.ObjectName
    ,CASE t.ObjectType
        WHEN 8259
            THEN 'Check Constraint'
        WHEN 8260
            THEN 'Default (constraint or standalone)'
        WHEN 8262
            THEN 'Foreign-key Constraint'
        WHEN 8272
            THEN 'Stored Procedure'
        WHEN 8274
            THEN 'Rule'
        WHEN 8275
            THEN 'System Table'
        WHEN 8276
            THEN 'Trigger on Server'
        WHEN 8277
            THEN '(User-defined) Table'
        WHEN 8278
            THEN 'View'
        WHEN 8280
            THEN 'Extended Stored Procedure'
        WHEN 16724
            THEN 'CLR Trigger'
        WHEN 16964
            THEN 'Database'
        WHEN 16975
            THEN 'Object'
        WHEN 17222
            THEN 'FullText Catalog'
        WHEN 17232
            THEN 'CLR Stored Procedure'
        WHEN 17235
            THEN 'Schema'
        WHEN 17475
            THEN 'Credential'
        WHEN 17491
            THEN 'DDL Event'
        WHEN 17741
            THEN 'Management Event'
        WHEN 17747
            THEN 'Security Event'
        WHEN 17749
            THEN 'User Event'
        WHEN 17985
            THEN 'CLR Aggregate Function'
        WHEN 17993
            THEN 'Inline Table-valued SQL Function'
        WHEN 18000
            THEN 'Partition Function'
        WHEN 18002
            THEN 'Replication Filter Procedure'
        WHEN 18004
            THEN 'Table-valued SQL Function'
        WHEN 18259
            THEN 'Server Role'
        WHEN 18263
            THEN 'Microsoft Windows Group'
        WHEN 19265
            THEN 'Asymmetric Key'
        WHEN 19277
            THEN 'Master Key'
        WHEN 19280
            THEN 'Primary Key'
        WHEN 19283
            THEN 'ObfusKey'
        WHEN 19521
            THEN 'Asymmetric Key Login'
        WHEN 19523
            THEN 'Certificate Login'
        WHEN 19538
            THEN 'Role'
        WHEN 19539
            THEN 'SQL Login'
        WHEN 19543
            THEN 'Windows Login'
        WHEN 20034
            THEN 'Remote Service Binding'
        WHEN 20036
            THEN 'Event Notification on Database'
        WHEN 20037
            THEN 'Event Notification'
        WHEN 20038
            THEN 'Scalar SQL Function'
        WHEN 20047
            THEN 'Event Notification on Object'
        WHEN 20051
            THEN 'Synonym'
        WHEN 20549
            THEN 'End Point'
        WHEN 20801
            THEN 'Adhoc Queries which may be cached'
        WHEN 20816
            THEN 'Prepared Queries which may be cached'
        WHEN 20819
            THEN 'Service Broker Service Queue'
        WHEN 20821
            THEN 'Unique Constraint'
        WHEN 21057
            THEN 'Application Role'
        WHEN 21059
            THEN 'Certificate'
        WHEN 21075
            THEN 'Server'
        WHEN 21076
            THEN 'Transact-SQL Trigger'
        WHEN 21313
            THEN 'Assembly'
        WHEN 21318
            THEN 'CLR Scalar Function'
        WHEN 21321
            THEN 'Inline scalar SQL Function'
        WHEN 21328
            THEN 'Partition Scheme'
        WHEN 21333
            THEN 'User'
        WHEN 21571
            THEN 'Service Broker Service Contract'
        WHEN 21572
            THEN 'Trigger on Database'
        WHEN 21574
            THEN 'CLR Table-valued Function'
        WHEN 21577
            THEN 'Internal Table (For example, XML Node Table, Queue Table.)'
        WHEN 21581
            THEN 'Service Broker Message Type'
        WHEN 21586
            THEN 'Service Broker Route'
        WHEN 21587
            THEN 'Statistics'
        WHEN 21825
            THEN 'User'
        WHEN 21827
            THEN 'User'
        WHEN 21831
            THEN 'User'
        WHEN 21843
            THEN 'User'
        WHEN 21847
            THEN 'User'
        WHEN 22099
            THEN 'Service Broker Service'
        WHEN 22601
            THEN 'Index'
        WHEN 22604
            THEN 'Certificate Login'
        WHEN 22611
            THEN 'XMLSchema'
        WHEN 22868
            THEN 'Type'
        ELSE 'Hmmm???'
        END AS ObjectType
FROM [fn_trace_gettable](CONVERT(VARCHAR(150), (
                SELECT TOP 1 value
                FROM [fn_trace_getinfo](NULL)
                WHERE [property] = 2
                )), DEFAULT) T
INNER JOIN sys.trace_events TE ON T.EventClass = TE.trace_event_id
INNER JOIN sys.trace_subclass_values v ON v.trace_event_id = TE.trace_event_id
    AND v.subclass_value = t.EventSubClass
WHERE TE.NAME IN (
        'Object:Created'
        ,'Object:Deleted'
        ,'Object:Altered'
        )
    -- filter statistics created by SQL server                                         
    AND t.ObjectType NOT IN (21587)
    -- filter tempdb objects
    AND DatabaseID &lt;&gt; 2
    -- get only events in the past 24 hours
    AND StartTime &gt; DATEADD(HH, - 24, GETDATE())
ORDER BY t.StartTime DESC;

Digging into Transaction log -- More advance ! Note the use of undocumented fn_dblog.


Find out the transaction ID

SELECT [Current LSN]
,Operation
,[AllocUnitName]
,[Lock Information]
,[Transaction ID]
,[Description]
,[Begin Time]
,[Transaction Name]
,[Transaction SID]
FROM fn_dblog(NULL, NULL)
WHERE [Operation] = N'LOP_DELETE_ROWS'
AND [AllocUnitName] = N'sys.sysschobjs.clst'
--- change here for the object name you think got dropped/deleted
--- can be table, stored procedure, etc
AND CHARINDEX(cast(N'ABOUT_TO_DELETE' AS VARBINARY(4000)), [Log Record]) &gt; 0 

Now find out the transaction based on the above transaction ID:

           SELECT [Current LSN]
           ,Operation
           ,[AllocUnitName]
           ,[Lock Information]
           ,[Transaction ID]
           ,[Description]
           ,[Begin Time]
           ,[Transaction Name]
           ,SUSER_SNAME([Transaction SID]) as CULPRIT_USER -- WE Got the Cluprit!!
         FROM fn_dblog(NULL, NULL)
         WHERE [Transaction ID] = N'0000:0000026c';






Excellent References :


The default trace in SQL Server - the power of performance and security auditing
How to read and interpret the SQL Server log by Remus Rusanu