Glitched mission objective

Ok so I’m sitting here playing borderlands 3 and
I’m on the mission where you have to get the gold technical from big Danny but when I killed big Danny he dropped the key over the side of the map and he wont respawns so I can kill him again and get the key please help

You’ll probably need to save-quit-resume. You may need to kill Danny again, but hopefully the key will be somewhere safe this time.

Happened to me too. Quit and restart.