Good point. Though parents may not really know. Then again, if they don’t know when it was swallowed how do they know anything WAS swallowed. So presumably if they DO know it was swallowed it follows they know when. (Am I confusing myself yet?) 
My point was more that the result (1 to 3 days) has been pretty well-known as the typical range of average transit times, for a long while.
