Can I ask what labels are on the wing fueling area?  All of the major fuel companies are supposed to have training and procedures, I'd slip a note in to whichever major company provides the fuel. You might get a free hat or something.  Nobody wants that kind of negligence to persist because it can only lead to trouble and they need to do an audit on this place.   Something went terribly wrong and needs to get fixed most likely.   I don't know if you can file an SDR over this incident, but i'd try.  I'd file a nasa report to get it into the database as well.

In Canada, we get slips off the fueling truck, printed at the meter directly, with all the density and temp data. The pilot either signs for it or gets a copy on his bill.   In the US, I find the ramp rat usually calls in the data to a front desk and that's a disconnect.

Many years ago the FAA mandated restricted filler plates for certified avgas planes.  But, they did not mandate the Jet nozzles to be the wide format to prevent kerosene into pistons even though it is FAA policy that FBOs use wide nozzles to prevent misfueling.

This is an interesting BP page on the subject of wrong fuel.  I particularly like the "no decal, no fuel" policy although I've never seen it in action.

http://www.bp.com/business/sectiongenericarticle.do?categoryId=9038531&contentId=7070677

Uggh, that's why I search for self-serve when possible.  

your report is a valuable reminder of what happens when away from the plane.