So yes the whole clip, not just the selection is restored in the browser when you hit Shift F.
As for the temporary trash file, that only seems to appear when you trash a project but not a clip.
When you trash a clip I have no idea where it goes. I assume the original media in a managed library goes with it and it just “disappears” altogether when you quit FCPX.
So it is a mystery where the files that get restored when you hit Shift F are stored.
Or is it?