As per the description, has happened to me 3 times now in a very short period of time.
Both a Diamond AIOT, and another persons Netherite AIOT seemingly at random just decide to vanish completely and without a trace.

No idea how to reproduce.

Another player in the server mentions it happened to them as well, around 4 times before the wipe on the previous version of the server.

I have managed to have this happen to me about 7 times now, but I still can't properly reproduce it on purpose.
And no, I am not accidentally breaking it, I suspected so as well for the first 3 times, but now it's very clear there is something else up, at one point it disappeared twice with only less than a minute in between, during which time I didn't even use the tool at all.

Anecdotally, I'm playing singleplayer, I got a diamond AIOT very early on from quest rewards, and it's reliably present so far (I've repaired it a couple times, etc.) If mine disappears I'll let you know what I was doing.

this happened to me also with my first AIOT and a couple of times with my MI iron hammers
they just disappeared out of my inventory magically
after that point my second AIOT is fully enchanted and netherited and still with me...for now (been a couple of weeks)