But the fact he didn't use it is proof they didn't go.
Who said he didn't use it? The astronauts routinely kept souvenirs from their missions, often in the form of bits of equipment yanked from the spacecraft. Lovell has the AOT eyepiece from Aquarius.
Conversely, much more equipment was manufactured according to spec than was actually flown. Something like 50 computer DSKYs were made, and are now lost or in private hands if they weren't flown. Something like 100 Apollo-spec Hasselblad cameras were manufactured. A spare flight-spec Maurer DAC wouldn't be out of the question according to well-established (if not officially authorized) practice.
The word around the CT traps is that they were props that Armstrong smuggled out from the movie set .
The problem with that theory is that all that junk is stuff that's part of the alleged cover story. Smugging out something from a set, to prove it was a set, would be equipment that would
only have been used on a set, not on a real mission. I have somewhere one of the "storage devices" used in
Mission to Mars. It's not a real storage device; it's a kluged-up bit of metal and plastic. That would be proof that
Mission to Mars was a staged story.
It would be nice of people actually thought through what constitutes proof.