Well done! There it is indeed, like it'd never been missing, a handsome door with 808 hung on it in brass numbers. Nestled between the pharmacy (807) and the glassware shop (809). It's hard to say how it was missed so easily before; it's sitting right there, plain as day. Like when you tear apart a room looking for a single object, only to find it sitting in the open in a spot you checked a thousand times before.

And just to make absolutely sure, the brass plate affixed next to the door does indeed say: DR. ALAN J. HILL: THERAPIST & PSYCHOANALYST.