Thank you for your post.... Hopefully the person will read it here and think twice before doing it again.
Unless there is an emergency situation I do not believe anyone has the right move your trailer, boat, equipment what so ever. Especially in a situation like this where it was not blocking anyone.
Even if this was done to allow for the movement of another trailer why not return it? Why put it somewhere the owner has to search for it?
Moving something that is not yours is simply wrong.
There was a conversation once about people moving another persons' boat to make room at the dock..... I wouldn't like someone moving my trailer...... Don't even get me started on touching my boat..