Back up, you left out some pretty important info. what date did the lease expire?
Were the tenants informed in writing that they had a date (prior to the loggers coming in) to remove their property?
Common courtesy would have required that. Anyway, you have THEIR stuff- give it back. You knew who it belonged to and didnt call them? Be the bigger man.
Now, if you (Uncle) sent them a reg. letter stating that if they didnt remove their property by a certain date you were not responsible as loggers were coming in (and we all know what thievin devils they are!). If that was the case then I think you have a small argument. Turn it around, how would you handle it?