They let you call in?
Mine made me drive 20 miles there to reserve it :-/
This seems to vary from store to store. I called around and among 3 different stores (all official Apple Stores) right near me...
* one said I could only do it by coming in-person into the store
* one said I could only do it online
* one said I could do it via phone, and indeed put me on the list right then as I was talking to them on the phone
Perhaps each individual store manager has the freedom to decide how they handle such cases.