Catch event of auto_shrink in SQL Server Log?
Pls see this link : 

To summarize (and this worked for me) :

Find out the location of your default trace file using :

SELECT * FROM fn_trace_getinfo(default);

Then use that to query your default trace file :

SELECT top 10 
    TextData,
    HostName,
    ApplicationName,
    LoginName, 
    StartTime  
 FROM 
 [fn_trace_gettable]('C:\MSSQL\Log\log_1110.trc', DEFAULT) 
 WHERE TextData LIKE '%SHRINK%'; 


You can see entries there for operations like DBCC SHRINKDATABASE etc.