RE: What would you do?
The biggest problem with just taking it is starting a war and having either your stuff or the land owner's, damaged or stolen. That said, I would take it and leave a note that it can be picked up at the land owner's house or at the sheriff's office. Give them a chance to come clean - could solve problems in the long run (or could serve as a first warning with the next leading to heavier trespassing charges).
Jason