While I was messing around in my world I noticed that blocks don't really disappear when breaking them while falling through them. But this only happens sometimes and only at certain points (or chunks) in the world.
The block (or rather the texture) vanishes after placing / breaking another block or reentering the world.

Steps to Reproduce:
1. Place down any block high enough to fall though.
2. Fly 2-3 blocks over that block
3. Let yourself fall and at the very last second break the block.