I would return to the store and tell them about the substituted returned items ... or at least the second one (you might make them suspicious if you tell them about BOTH occurrences). If you don't tell them, you'd better stay out of that store. Also, while you are waiting to see if your CC is credited and you got away with it, you could be arrested tomorrow at your home (after they get your address from your CC company or your license plate).
I speak as a former shoplifter who was arrogant, gambled, and got caught. If you don't tell them what happened, even if the subsitutions were accidents, you are a shoplifter since you are cognizant of what really happened. And while you might very well be good at shoplifting, I guarantee you they are better.

