That seems like one of the more unlikely causes, among the almost infinite variety of causes that are consistent with "several people said they can't find some files".
To me the most likely one by far is the deletion was actually commanded, for example by a flaw in the program they use to sync, or by malware.
I am still skeptical that users are correctly describing the behavior of a multi-party synced filesystem, or that Drive for Windows is bug-free. You seem to think it's a flaw on the backend but I think there are many other possible causes.
To me the most likely one by far is the deletion was actually commanded, for example by a flaw in the program they use to sync, or by malware.