Well, I may be tending towards the obscure here; but it seems to me that in hotels, offices, and other places with public access, certain ordinary phrases acquire local "proper noun" status.
In a hotel, for instance, the phrase "room service" functions as a proper noun; as does "sales & marketing" in a business; or "left luggage" at a railway station.
By which I mean that in those particular contexts, you can say "I'll have a word with Room Service", or "have you spoken to Sales & Marketing", etc.
Similarly, the Notting Hill carnival in London is referred to as "Carnival" by local people, rather than "the carnival".
These phrases often take initial capitals: thus "room service" may be presented as Room Service in the little folder about the hotel on the table by your bed.
It seems to me that "Coat Check" is a member of that happy band.
MrP