Check which shopping mode you’re in. If you’re in the “Order online” mode, your basket serves as your shopping list. You should find all the products you added to the shopping list there. If there are multiple lists, look for the name of the shopping list you’re searching for.
Once you switch back to the store mode, the shopping list will reappear instead of the basket.
If you still can’t find the list, it’s possible that someone deleted it. Shared lists can only be deleted by the person who created it (admin). The list will disappear from your account without notification.