Grab & Go tracks stock per location (via the Stock module): when you pick a pickup/delivery location, the page's underlying query sums that location's available stock for every meal, and if a meal's total stock at that specific location is zero or less, it's removed from the grid entirely for that location — it isn't shown as "sold out," it simply doesn't appear. The same meal can still show normally at a different location that has stock. This is separate from the menu-availability rules other modules use (delivery day, cut-off, category), so a meal missing from Grab & Go doesn't necessarily mean it's off the menu elsewhere.