This bug, that ive nicknamed "Schrodingers Villager", is when a Villager is put into a boat, and vanishes if you get too close to it.

HOW TO REPLICATE:

Create a New Superflat World, only changing the grass to be Blue Ice.

Get a villager inside of a boat, and put the boat onto a path in the village.

If the glitch is replicated successfully, the villager should disappear when you get too close, and reappear when you back up.