Question: What is the ruling on using the property left by unknown owners in hotels, university dormitories, etc.?
Answer: If you know that the owner has given up that property or is satisfied with your using it, there is no problem in doing so. Otherwise, it is not permissible to take that property unless you intend to take it to its owner, in which case you must keep the property, search for the owner, and give the property to its owner after finding him. However, if you are disappointed with finding the owner or it is not possible to reach him, you should give the property or its price to the poor.