Why????

They may have been having problems with mobile meth labs. That's the new big thing from what I've been reading. Farmers have even been having their fertilizer chemicals stolen by these dirt bags and this farmer may have had some activity around his property.

They were most likely just doing their jobs. I would've asked if it was OK to take a few more pics of your car for a website and they would've most likely said why they were suspicious.

Of course, I'm a "The glass is half full" kind of guy and like to think the best of a situation.