Unfortunately I would say, yes (although I am technically not that deep in the database structure). These backup databases are very fragile, even a damaged sector within can sometimes be enough for disaster. So meddling around be deleting files calls for
it. (Usually one assumes, that the client needing restore and the backup database are not dead in the same time, but with bad luck this may happen.)
Failing to undelete means you deleted them not via the recycle bin? Also the real files may have been stored not on D: bot on another physical disk so that the undelete did not follow up the proper file, only the tombstones, maybe.
In which manner the harddrive on the PC crashed? Was it a soft crash or is it physically dead?
If the first you may try to attach it as secondary disk to another PC and try to recover the data that way. For a physically dead drive only the costly data recovery services would be an option.
Best greetings from Germany
Olaf