We take great care to make sure that meals are always ready when you are, so when we stock out of an item, it's often due to unexpected demand or other unforeseen event that impacts our ability to make or ship meals. That same unpredictability is why we don't list ETAs for restocking; it's not that we are keeping it a secret, it's more likely that we don't know just yet.
Emailing us to ask when an item is returning isn't going to provide a different answer (though we always love chatting with customers).