If you haven't emptied the recycle bin since deleting them then they're probably still there somewhere. Could you have moved them to another folder accidentally?
You might want to do a search for them.
If they are really gone and you have TimeMachine turned on then you can get them back from TimeMachine. Otherwise you're going to need someone to recover them with some type of disk recovery software tool (you might be able to download something yourself, but any new files you create on the machine could potentially overwrite the old photo data on the disk (extremely unlikely, but possible)).