Restroom Pass

Today, I had a restroom confrontation with a parent. Her child asked for a pass to the restroom at the beginning of the period. He was told no and went back to his seat. During the remainder of that period and the following one, he never mentioned it again. He participated in all classroom activities and laughed at jokes other students and I made. He even stayed after class, asked me about pre-approval of a book for his book report (the due date for book approval is next Wednesday), and discussed the reasons why I should disregard my better judgment (and the time frame for the assignment) and approve his novel. He waited for me to help a student who had to catch the bus and a girl who was in front of him in line. According to his mother, when he got in the car, he told her his stomach was hurting because I would not allow him to go to the restroom. Typically, when a student asks for a pass during that period I initially do not allow them to go because another group is at lunch during that time. (There have been problems with students going to hang out with friends rather than going to the restroom.)However, if they ask later on, or they tell me they really need to go I allow them to. Neither of those things happened today. The parent was livid and did not calm down until I had relayed the course of events twice and made it clear that her child was not being singled out. I also told her that I do allow students to go to the restroom, and her son has been allowed to go.
I have only had this happen one other time during the eleven years I have been teaching. The secretary asked if this was a quiet student that might have afraid to ask again. Considering his defense of his book choice and participation in classroom discussion, the answer is no.

I hope this is not about me not approving the book, or him upsetting her because he asked to stop at a restroom during the drive home.