Let's say few years ago I lost/forgot a photo camera in beach, and I never reported it as stolen because I lost it and it's my fault, nobody came and took it from me with a knife.
I am not going to put guilt on someone else for doing something wrong, when I was simply careless.
There is a big difference.
If you think that any thing someone found was stolen in the world, than we are living in world that stole 99% of things and land from other people.
It's not the same if I found a piece of land nobody is using, and if I kill someone and take away land from him.
To conclude, I would personally try to find original owner of paper wallet.
After reasonable amount of time I would give one part to charity or poor people, and I would just stake rest of the coins for future.