I'm still thinking just the key.
I know that the ignition switch going bad leads to weird things going on (search 'ignition switch and radio)...just read about this a week or two ago here.
Since this all started with the key...I'd start there (find key!) and just chalk it up to another bmw weirdness.
Upcoming comedy shows: May 20, Greenwich Village Comedy Club. 6 p.m. See Facebook for other shows and PM me if you can make one...love to see you there!
A recent set: https://youtu.be/995gLmVEVZk
Mangofy your E46!