>>7882656 (LB)
Not sure if you understand just how big Chateau Marmont is.
Staircase is pretty small. Perhaps there's more than one.
It's also not unheard of for hotels to have private floors.
We only see a handful of channels.
Tunnels
From an article on James Franco's house:
There’s also, reportedly, a now-sealed-off backyard entrance to a secret tunnel that led to the infamous Players Club on Sunset Boulevard.
https://www.yahoo.com/lifestyle/home-week-live-next-hollywood-140026802.html
From an article on The Players Club:
And, if he or one of his famous friends wanted to finish the night in more comfortable accommodations, legend has it there was a tunnel connecting The Players straight up into the decadent arms of the Chateau Marmont.
https://www.kcet.org/food/the-players-preston-sturges-screwball-times-on-the-sunset-strip
Plus we know many (all?) the houses up in Laurel Canyon (directly behind Chateau Marmont) have interconnecting tunnels
We know there's tunnels associated with Mitzi Shore and the Comedy Store via Joe Rogan of all people