> Restaurants have suddenly become unavailable, my demand for them has dropped precipitously, they become available again, but I don't see myself reverting to my prior demand for years, if ever.

That's not considered a demand shortage in this context, because you're not necessarily holding on to more cash (the medium of exchange) simply because you've stopped going to restaurants. You might be dispensing of your cash in other ways.[0] It's a negative supply shock that's confined to the restaurant sector.

[0] (Yes, there is a multiplier effect but it goes both ways. The multiplier effect is a result of agents trying to keep to their preferred level of cash holdings while facing an outside change in the amount of monetary spending. It's really a "hot potato"/"frozen potato" effect: if agents are suddenly giving you more cash you'll want to spend the excess, and if no one is giving you any money you'll seek to restore your balance either by seeking cash from others or by curtailing your own spending.)