I found 100 Riyals in the street a year ago and I took it. I have announced it for a year without anyone coming to claim it. What should I do with it?
If the reality is as you have mentioned, and that you have announced it for a year in the Shar‘y (Islamically lawful) manner, it is like the rest of your property. If one day its owner appears, you should give it to them. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.