I'm also having this same issue. It's happened at two separate venues. The first was on a date at a restaurant. My sims requested a table, were seated and placed their orders. While waiting for their orders they stood up and it appeared i needed to request a table again. I did so but this time all the tables began to disappear every time I would place an order for food. Each table disappeared..
The second time was at a wedding venue where the sims had tried to use the "serve all" commands on one of those round buffet tables but that table also disappeared upon using the command. Then other tables that my npc guest would request to sit at would disappear.
It's happened at two separate venues for me.
[CM - Edited to merge replies]
