I had pwd in "tools/path", "../path2" existed, and I moved a file this way:
<verbatim>
fossil mv myfile ../path2
</verbatim>

Instead of renaming to it renamed to "tools/path2", and the "fossil status" started showing "NOT A FILE".

I had to "fossil checkout" to fix that working directory, and specify the full rename path the next time, including the file name.