when i used to change tires at a shop we would take all the wheels off at the same time. we didn't mark them when they came off the car or anything, so chances are they were put back on the car in different spots than they were originally. never had a TPMS system go haywire because of this. hope that helps.
if your light is coming on you either have low air pressure or one of the sensors may be loose or defected.