Lunch Money? Gone?

Yesterday I gave Archer $20 for his hot lunch account and told him to give it to his teacher. The envelope was among a big batch of other paperwork and envelopes for various school fees, I figured he would just hand the WHOLE BUNCH over to his teacher and all would be well. I under estimated my son's willingness to decide for himself what to do with the paperwork...
Today the hot lunch person was claiming that they never received the payment. This really bothered me because since last school year I have been contesting what we owe them for Archer's lunches. (They say we owe $4.00. I say we already paid it.)

So tonight, just to double check, I said, "Archer, are you SURE you gave your teacher ALL of the envelopes?" (PTA membership fee, book rental fee, LUNCH MONEY) and he said "Yes... except for the one for lunch money." WHAT? Why didn't you give it to her? Where is it? "In my desk. Cause I brought my lunch box." So I then explained that the breakfast he had at school also costs money and he said "But the envelope says LUNCH!" The boy may be getting too smart for his own good. Or for MY good, since aparently I didn't count on him taking matters into his own hands!