If you are running any reasonably modern version of Zenphoto there is an album rename option on the album's tab, so I guess you either are pretty behind or did not look so well.
The method you chose to use--creating new versions of the images by copying them--did, of course, not replicate any database information of the old images. (How would Zenphoto know your intent....)
If the database still seems intact, a "refresh database" or "refresh metadata" might straighten things out. Not sure.
Have you a backup of your Zenphoto installation? (I do not remember when the backup/restore utility was launched, so maybe your install is prior to that.) If you do, use the restore function to restore the DB as it was.
BTW, it is just for this kind of situation that I personally store all information about my images--descriptions, tags, etc. as part of the image metadata. Then for sure it travels with the image no matter where it goes.