Follow Up and some notes ...
One cannot see the 'recyclebin' link in course admin menu or anywhere at Category level in Moodle Admin UX.
So it looks like method described is only hope.
Commands that were shown you should be able to do with any tool you have to browse files.
** IMPORTANT ** ...
Recyclebin has lifetime of 1 day by default.
So to do/use recyclebin info, do it in one day!
After which think the file gets moved to trashdir and then there is no more references in the DB for you to seek/query for the location of that file.
moodledata/trashdir/ however has same structure as filedir and if you look long enough in there for files and sizes of files (your backup probably a large file) one might find what is really a backup .mbz file.
Again ... best of luck!
'SoS', Ken