Strange. At the end of last week I also noticed that @duerer ‘s rear axle master file ended up in my root Google Drive directory which google tells me isn’t even a shared directory 🤔
I’m trying to work out this issue now and running into trouble. I can’t seem to delete nor relocate the offending library because it’s “indirectly linked:

As far as I can tell something is using a material from within that file. Yet even setting the users to zero doesn’t appear to solve the issue…
I’ll continue trying to figure it out. Though at worst, if it doesn’t go away, it doesn’t appear to be consequential to anything. Just a minor annoyance to get a warning and know a linked library is broken.