With some lizards (as I've at least noticed with my geckos and chameleons) you sometimes won't even notice shedding. I haven't seen some of my geckos shed ever, and if I do its always been due to some kind of illness/low humidity where the shed wasn't moving along properly. Somedays I'll notice my cham turn WHITE, and then the shed will be off the next day, or I won't even see him turn white and the flakes of shed will be along the bottom of the enclosure...
Its probable that he has shed before, but you haven't caught it
Shedding usually takes one or two days max (in my experience) and misting can help increase humidity and allow them to shed with more ease....just don't pick at it