Forceloaded chunks are volatile and lost on reload in newest snapshots.

In 19w02a and 18w50a, forceloaded chunks are no longer listed when doing /forceload query and do not forceload the chunk.

Steps to repeat bug:

1) Forceload a chunk (/forceload add 0 0 0 0)
2) Close your game and reopen the world
3) Do /forceload query and you will see it no longer listed.

This bug doesn't affect 18w49a and below so it must have been causes by one of the bug fixes from 18w50a I assume.