What version of Moodle?
IF a version that has/uses 'recyclebin' what's been deleted might be in a .mbz file whose contenthash (which is location in sea of files in moodledata/filedir/).
Query of DB:
mysql> select contenthash,component,filename,filesize from mdl_files where filename like '%.mbz';
the contenthash tells one the file location in moodledata/filedir/
example: 7076296142de12818f4b55e692dbb8a32452b319
[root@sos filedir]# pwd
/var/www/moodle38data/filedir
[root@sos filedir]# find ./ -name 7076296142de12818f4b55e692dbb8a32452b319
./70/76/7076296142de12818f4b55e692dbb8a32452b319
If the ./70/76/.... file shows it's gzip compressed data, from Unix
[root@sos filedir]# file -b ./70/76/7076296142de12818f4b55e692dbb8a32452b319
gzip compressed data, from Unix
You could copy the file located at: ./70/76/7076296142de12818f4b55e692dbb8a32452b319 to some directory outside of moodledata and rename it 'somebackup.mbz'. Then use that file to restore to a new course.
Hopefully ... that would work!
Good luck!
'SoS', Ken