Some time ago, I found a zombie villager.

I cured it, and dig up a 2x2 square for him to stay in.

Everything was properly lit up, there was no way for lava to get in or anything similar

As soon as I had the chance, I placed a library-like block that I can't remember how its called, to convert him to a librarian. It worked. I went to my close sugar cane farm to get some emeralds, and by the time I got back to the villager, it, together with the library-like block, disappeared.

There was no creeper explosion trace, as the square he was in was intact.

Literally it's like somehow the villager and the block I placed in his square despawned.

Notable facts:

He was deep in my mines, no sunlight touching him (Did he become a vampire, transformed in a bat and fly through the half-blocks I enclosed him in? (no, I don't have mods))

he had no bed (did he die from lack lf sleep? (i was jocking, but, can this actually happen?)

c;lose to bedrock