If you try and explicitly stash a file that isn't being tracked, you get no warning.

<pre>echo "hello" > test.txt
fossil stash save -m "Test stash" test.txt   # Would expect an error when running this line

# I managed to do the following:
echo "world" > test.txt
fossil stash pop</pre>

And blew away some work.  My fault for not having committed the changes, but silently failing definitely seemed like note-worthy bug.