The Mystery of the Disappearing Pants

Sammy has some sensory issues, well a lot of sensory issues actually. He has a lot of rules for clothing, especially pants. His pants have to have a drawstring, be soft, no buttons (not even fake ones), elastic waist, he prefers them to be blue and they cannot make any noise. I bought 5 of the same pants to add to his other 3 pairs he would agree to wear.

 I am down to 2 pairs. I don't know where they are going but they aren't in the laundry, or in the bathroom, or in his room... or anywhere I can think of. God i hope he isn't throwing them away!
We had a similar issue with his socks. he would go to school with them and then come home without. It took forever and some stealth work but we figured out he took them off at lunch and threw them away. He obviously cannot do that with his pants.
So where are they going?