(My story: just last week I fixed a temporary profile issue for an acquaintance and all that had happened was that Windows messed up the connection with her online Microsoft account. After signing out and in again, it worked fine. I was surprised at first because I wasn't aware that such a thing as temporary profiles existed. It became clear that she was working on a wrong profile once I opened a shell and the path before the prompt said "c:\users\temp".)
There are definitely warnings that any work/data stored in the temporary profile would be lost, so maybe they did not take these seriously enough.
The only thing that I actually find absolutely unforgivable is that the temporary profile is named after her normal account. Creating temporary accounts with ample warnings, yeah, not great. Pretending to be the profile of the user...? Nope