The checklist has the solution for "Strange odor in cockpit"
1. O2 Masks -- ON . . .or tell the guy the law is overflowing, why don't you/he go back and check (hint hint) ...
For the current guy, just call on freq and say your Captain just jumped out. Oh sure it will look like he put up a fight, but that can be explained by impact, or maybe he hit a barbed wire fence or a bird on the way down. You can explain your bruises and scratches by saying you tried to give your cat, Bruiser, a pill the previous night. The investigators, if they've ever owned a cat, won't ask why the cat has disappeared. (No self respecting cat from h*ll ever takes a pill, nor returns to someone that wants to give it one) The scratches, tears, and broken plastic inside the cockpit can be blamed on turbulence - make sure you turn the autopilot off before the incident so the ATC flight path will jive. Finally, be sure to scream "[Captain's name] what are you doing?! Close that door! No!!!!" several times, at least loud enough to cover his screams, for the CVR." It will help if that takes place after a discussion about the foul odor coming from the lav and he decides to go take a look.
For those not smart enough to know satire, don't try this at home.
Fly SAFE!
Jedi Nein