I'll assume that you are talking about photos that were in the camera roll, but not imported to the computer? I understand there is some software that would allow you to look into the backup and possibly extract the photos, however if you have made a backup since then, it is my understanding the backup process overwrites the last backup when it makes a new one, so you may not have the backup available to look at. I believe for the Mac one of the programs is phoneview, or something like that. I don't use Mac, so I'm not exactly sure on the name. It should give you enough to search by though.