My partner dropped her wallet while walking the dog in a big park near us. Thankfully someone brought it to the police station and they gave it back to her. I could never take anything I found like that. Once we found 50euros in an envelope on the street. We also notified the police and a few hours later a sweet old man showed up at the door with flowers to say thanks. Made me feel really good. We were slightly tempted to keep it as we had no money ourselves at the time, but doing the right things just feels good in my opinion.