In that case, they should throw in some biscoffs with that mail delivery.

In all seriousness, while annoying, I doubt you'll get much for complaining. I'm assuming they were able to wrangle you up some snacks of some sort being served (or purchased) in the main cabin. If you got some form of food, you'll get a few skymiles if you complain. If no food at all, then maybe some more miles. I doubt a voucher or partial refund will appear, but who knows.

Pretty crummy situation though. I've never had it happen where they ran totally out.