Sorry Barcas, but this is exactly what I disagree with when it comes to lost discs. Instead of offering a "punch in the face" for not returning it, how about offering a reward for it's return?
So many discs get lost and never returned. We need to encourage players to return discs.
Assuming that they kept it on purpose and threatening them with bodily harm is probably not going to be constructive.
If I see someone on the course with your disc, I will offer them one of mine in return and then I'll track you down to give it back to you. Now, if someone comes up to me and punches me in the face, I'm going to owe you the same in return.