I had put a bunch of white stained glass in one of my buildings and logged out. I went back into 1.6.4 for a bit, and when I logged back into the snapshot most of it had disappeared. The blocks were random that disappeared. 🙂
MC-34783
Stain Glass Disappearing when loading world with 1.6.4
Resolved
Works As Intended
0
This is not a bug. It has to do with block ids. The world will delete any ids that do not exist. You risk this problem when opening a world with blocks in a version before those blocks were added.