Hello
As all other people have said, I agree its Essential Practice to Backup Database after Rsetlogs.

There may be a way out from your scenario to recover, If your database was in archive mode and you have all the archive logs with you from the day you had taken cold backup of your database.

Restore all copies of your all datafiles
Perform recovery till cancle or till time (Time just before you took your datafile offline earlier)

Regards

Mandar