It looks flat, like it's meant to be part of the ducting. I found it by accident.
Found the garbage chute -- it's in misc/misc.
How is the neighbor hiding supposed to work? It seems to do something different on every lot I play. .... In the Cho lot, it was blacked out, but I could still see them walking around and doing things in there.
We've been discussing the Cho/Riley lot in the AL bork thread in the 'You Broke It!' forum -- that lot is borked, but the fix is simple. Just have whichever sim you're playing visit the other for a bit. When the playable leaves, the other lot returns to 'normal' and becomes invisible.