Is this stealing? Yes and no. It’s kind of tricky when you talk about things that were forgotten/lost. It’s kind of a slippery slope.
Like with my daughters, they often find something in the floor and then claim it’s theirs. They found it, someone else lost it or forgot about it. Well, that doesn’t make it theirs. It just means someone lost it. While it’s common in our world to simply take things that are found, ‘finder’s keepers’; the bible holds us to a higher standard. “And as you would that men should do to you, do you also to them in like manner.”
For me, if I lost something I would at least want someone to attempt to find out who it belonged to. I’m not sure I would care about a hockey puck though. Just as I often leave golf balls laying when I can’t find them.
But there are other variables. Is it a public ring? A school ring? A private ring? Where you supposed to be there or just wandering around? It’s much different to walk through a field at night and find a golf ball, and to walk into a place where the establishment(owners) pay for the equipment. To them it might be a very big deal to lose a few pucks. Especially if they can’t afford new ones.
So I would let my conscience guide me. Do you feel a need to return them? Do you feel like you have stolen? If they were your pucks, how would you want someone to deal with them?