I was about to say... From the picture you put up of your barn weeks ago; looks like you have to go all the way down the drive, past the house to get to the barn.
For people to even know if anything was even in there; people either know you and your hobbies, or the barn doors are open all the time with your stuff right out in front to see from the street (which I doubt you do).
So for someone to drive their vehicle up your driveway up to your barn in the hopes of finding something good in there I found a little strange (yes I realize there's nothing "strange" when it comes to crackhead behavior) but most thieves will do some kind of recon before bringing a vehicle to collect. Makes sense it was someone you knew.