When David is folding clothes,he sees Michael's "Captain Astro" underwear and teases him with them. Michael quickly grabs them and refolds them. As Michael is about to leave for work,David pulls him in for a kiss. In the very next moment,we see a close up of Michael's face. As he turns towards the door,you can clearly see the underwear in David's right hand.
The bank teller can't know which check numbers have NOT yet cleared simply by viewing Michael's statement on the bank's computer. He would have to see Michael's checkbook register too in order to make the comparison.