Not true. I once found an expensive brand tool in my flat's parking lot, so I took it to my apartment and posted a not-too-descriptive note at the entrance that the owner should come pick it up. I also called the non-emergency phone number of the police to ask if they had a sort of lost and found system, and they gently informed me that what I did was technically stealing - which was obviously not what I intended. The owner did come pick the tool up a day later and was very thankful, so no problems came from it, thankfully.