Passive mobs despawning in 1.17.41

Okay, It may just be me, but it affects villagers, but I m certain that this bug is real, firstly, I had a mending villager disappear, then most of my villagers disappear to, then a whole my 7 sheep disappear, in the villager area, the place is not safe so it may just be zombies killing them, which I get it, but hold on a second, some people may say, ''what if a wolf got there'' then I said, ''there is no surrounding blocks in the area of my sheep pen'', then other smarter people came in, and they said, '''what if the wolf spawned in the pen'' well I said back to them, ''Wolfs can't despawn, even when its in the agro state'', if this is not a bug, then figure out how the wolf got out, and I know wolfs can attack trough fences, but THERES NO SINGLE SHEEP LEFT, and my sheep pen have atleast 4x4 area in the middle