If I recall my Crim Pro class correctly the cop needs a reason to believe (50%+ chance - AKA probable cause) that you have committed some crime (no matter how slight - even vagrancy) to detain you. But I think he would have come up with some sort of story that would be plausible in the community in question - especially in retrospect - so as a practical matter you would have no case.

Especially while touring, I view law enforcement as a source of physical security and never fail to wave (with all my fingers) at all officers on the road and saying hello to those lying in wait along the side of the road. I've also had offers of water and suggestions for camping.

Now officers are human too and there's a whole range of attitudes out there. To maximize positive outcomes I smile, am friendly, I am helpful, I will provide identification, and I would allow a patdown. However, being the civil libertarian that I am, if I were to be asked to submit to a search of my bags, I would politely refuse (Yes, I suppport your war on drugs, but I'd rather you didn't search my bags), but do absolutely nothing otherwise to provoke the officer. There's an infintesimal chance that the officer could plant contraband, but if you've been cooperative up to that point, you would have given him no reason to do so.

Encounters with law enforcement require that you mind your P's and Q's. Bear in mind that in a country that sponsors Abu Ghraib, Guantanamo, and the Patriot Act, your Constitutional rights not guaranteed.