How to find user who Drop any thing without auditing applied on database
Please try it:

Select * from user_audit_object


And for restore dropped table , you should know , that drop did without purge command.
If he/she used purge you can just restore your object just with dump or flashback and if he/she didn't use purge you can use this select * from dba_recyclebin where orginal_name=&lt;object_name&gt;, if the select has result you can restore that and otherwise just falshback or restore backup