If you are in the UK, you can take him to your local small claims court, I guess you can do that in the uk also. Tracking him down is pretty easy.

Pete takes the devaluing of copyrighted material extremely seriously, He does not treat the subject as a joke and I would suggest that if he took your material without permission then as far as Pete is concerned this is a very serious matter, one he would have thought about a lot before doing so.

So personally, I would take this matter very personally. After all, you make your copyright claim very noticeable, you don't go around hiding such stuff in the hope that you can catch people out in order to sue them.

I would say you have a very strong case, and that (I guess) if you do not sue, then you are accepting the devaluing of your materials by a third party without permission.

Not that I think the throry is correct though.