One thing I will add that may contribute to circumstance. The only time this has happened to me (massive impact though) is I had been in the nether and there was very noticeable unexpected delay glitching that was impacting both of us (multiplayer) for no known reason. The type of delay glitch that occurs when wifi signal is weak, but not the case here. Nothing strenuous from world/build perspective, just wandering around.
Returned from the nether with no issue (placed netherite armour on a stand which was one of the victims of this bug), saved and quit as per normal. On next load the armour and stand as well as many animals, villagers and mine carts (all local to my home) were gone (not all but the vast majority. 90%+).
Commenting here as I saw earlier a query as to whether this occurred after glitches/issues so it may be relevant.
I feel for you guys, major bug impacting a lot of people and a lot of hard work. Good luck!
iPad 6th gen (2018). Render distance 9. Multiplayer world hosted from an iPhone XS.
Already posted to this thread, but this bug has struck again (fourth time in total).
This time though, I was building a rail cart from my home to a village 1400 blocks away (sole purpose was to cart back villagers to repopulate my crafted village next to home which is empty due to this issue). The village 1400 blocks away was very populated. Several in-game days later as I built the rail system then on the final journey with the rail system fully completed the village was empty aside from one iron golem and a cat.
I know we’re not meant to express frustration here, but this is soul destroying.