MC-15913 was never resolved adequately. The game "forgets" the last minute or so of activity prior to save and quit. The blocks I placed before I saved just disappear. This is the third time this has happened.

[09:25:29 INFO]: Minecraft Launcher 1.5.3 (through bootstrap 5) started on windows...

[09:25:48 INFO]: Looking for orphaned versions to clean up...
[09:25:49 FATAL]: Fatal error launching game. Report this to http://bugs.mojang.com please!
java.io.FileNotFoundException: File 'C:\Users\Chris\AppData\Roaming\.minecraft\assets\indexes\legacy.json' does not exist