You don’t need to disassemble anything in order to remove the battery! You just unclick the back cover.
Also, there is a known issue for some users with a “pogo pin” dropping out of the phone if the phone is actually disassembled e.g. Disassembled my Librem 5 and this fell out (has photo) so I just want to confirm that you are talking about a screw and not a pogo pin.
Regardless, a photo may give more clarity as to what you are referring to.
Maybe review: Disk decryption passphrase - #26 by veleno and subsequent discussion for what is an acceptable disk encryption passphrase and what will possibly get you into difficulty.