There is another black weapon box near emercom extract that one always gives me a lunch box as well deffo going interchange next wipe for that quest lol, also I don't think he was a cheater if he was you would of just got 1 shot headshot and never even knew where he was.
Interesting I don't know where that weapon box Is but next wipe that quest will be really simple to complete. From my understanding cheaters can toggle which body part they want their aim to lock on to which is why only thorax hits from that distance made me suspicious. No way to know for sure though just gotta keep trucking along. Btw I really appreciate you taking the time to watch all these videos! Glad you're enjoying them :)