That sounds a pain, and the fact that it's not typical isn't going to make it feel any better.
Where were the photos stored? If on a removable card you can use a cheap card reader and any file recovery software to restore them - just don't write to the card in the meanwhile as you may overwrite the data. If on the phone's internal memory it's much more problematic: if you can mount it as USB mass storage then that's fine, but if you only have MTP to connect to a computer (as is normal in android 4 onwards) then standard file recovery utilities won't be able to get the access they need.
When you say "can't delete" do you mean not at all, or that they reappear after deletion? Which raises another question: did you have any cloud backup of the photos active? So many cloud storage tools want to back your photos up these days that it's worth checking whether you allowed any of them to do so.