Thank you very much for responding.
Here are the sequence of events:
4/18 9:00 pm A full backup was taken of the Db
4/20 3:00 am The database was restored from a backup of our production database (a routine, daily process)
4/20 1:00 pm The data was refreshed with production data (and the routine restore job was disabled to allow a long-term test with a static Db)
4/20 2:00 pm A transaction log backup was taken
4/20 4:00 pm A transaction log backup was taken
4/20 9:00 pm A differential backup was taken
4/21 10:00 am - 4:00 pm Transaction logs taken ever 2 hours
4/21 9:00 pm A differential backup was taken
4/22 10:00 am - 2:00 Transaction logs were taken every 2 hours
4/22 3:00 pm - Users discovered a problem with one of their testing processes and requested a restore to 2:00 pm
We began the restore by backing up the tail of the transaction log. Database is now in a "restoring" state.
Then we began the restore through the GUI. The restore set offered by the GUI backup process included the following files:
4/18 9:00 pm Full Backup
4/21 9:00 pm Differential Backup
4/22 10:00 am - 2:00 pm Transaction Log Backups
It was at this time we received the error message indicating the differential backup was not the same version, and it dawned on us that the full backup we were using for the starting point was basically from an entirely different database and the integrity of our backup set was compromised.
At this point, if we can rebuild the "starting point" and apply all the transaction logs, I believe we have all the data.
Since we started the restore, the database is now in a "restoring" state, and it is my understanding that there is no way to cancel the restore and just return the database to the state it was prior to the restore. Can you confirm this? Also, are there any other options you can think of that we could try if we are unable to rebuild a full backup and restore over that with transaction logs? Any "ROLLBACK" options for example?
This is not a production issue, but it is a critical testing database utilized for a MTP with an extremely tight deadline. If we don't have to lose 3 days of testing, we would be very relieved, but the longer it takes to figure this out the fewer options we have.
Thanks for any suggestions you can give!