I just watched that part of the episode again to see what happens.
Bubba's driving the RV, and Squirt's in the back with Loretta and Leona (although Leona disappears after briefly appearing reflected in a mirror). Cindy peels out of the Boar's Nest parking lot and is seen quite close behind the RV in its next couple of appearances. After Bo and Luke crash into the haystack, the blue car is further behind the RV but still following. The car isn't shown in any of the shots of Loretta dropping the pictures - the inside shots only show the curtains at the window, and the exterior shots only show the rear of the RV. The only explanation for Cindy not spotting the pictures is that she either dropped further back or took a different route to the barn, but both seem unlikely given that the car is shown pulling into the barn just behind the RV.
On a related issue, I've just noticed that the window at the back of the RV where Loretta drops the pictures has light-colored curtains which split in the middle when viewed from the inside, but a dark-colored blind from the outside. Although it's possible to have both, the curtains let in too much lights for there to be a blind too.