Missing food

This isn't a Bug, rather the game working as it was meant to which is why blocking the door or 'closing' your restaurant is never recommended. The game is built on the idea that we have a constant flow of customers entering and exiting our restaurant.

As far as I understand it, it works like this: When you block your door, the game still thinks that customers are coming and going at the same rate as when the door was open and (even though you can't see it) the game thinks it's still selling food the entire time so when you unblock the door, the game has to scramble to try and tally up all those sales it thinks it made while the door was blocked. This can cause all your food to be sold in one instant in what we players refer to as a Quick Sale. These sales might not happen every time you block your door but it is always a possibility which means blocking the door is basically a gamble.

If you're worried about your customers walking away angry at the lack of food, you shouldn't sweat it. The meter that counts happy customers doesn't affect anything in the game, I think it's more of a way to let us know if we need to add more food or seating to our places. Once you get food back on the counters, the meter refills entirely within minutes so there's not a lot to gain from blocking the doors - but that's just my opinion.