Re. lunch breaks: In many cases, I think, there is only one person in the office, such as the manager, who can sign off on an item of business. When that person goes to lunch, nothing can get finalized anyway.
And in addition to that - since when do you have to pull a number there? Until now I always filled up my shipping form, submitted at the counter and sat down until it was my turn. Can't remember if I'be ever been there around lunch time yet but I would also at least have reacted surprised and unpleased having been turned down like this.