Re: Stolen ?
Stolen is right IMO, taking something from somebody else without their permission.
It does not matter if it was in a publicly accessible place.
As an example your wallet is in a publicly accessible place most of the time when you are walking around. I bet you would still call it stealing if someone took it from you (probably not without a fight / chase if you noticed).
If it's not your's you have no right to take it unless given permission. It being visible to you does not give you that permission.