Ever since a disaster with a Dropbox configuration in 2011, I've only relied on myself and not on anybody else to keep my files safe and available world-wide.
If you want a guess, it probably was related to pruning old accounts/old files.
> Google Drive deleted six months worth of files. Here’s what happened and the fixes.
I think the "six months" is coming from the original report but looks like it could be longer.
https://support.google.com/drive/answer/14286582?sjid=464734...