It doesn't matter if it has a pdga number on it. It's not your disc. If you found someones wallet would you just take their stuff out, throw it away and keep it? Just because you don't get yours back, doesn't make it right. I have lost several and not gotten them back. I can't justify it to myself that I deserve to keep what's not mine because I didn't get mine back.
if you walk away from it, its there for someone else to salvage.