Commiserations. That's really disappointing. No possibility of rescuing bits to eat here and there? Was it your first time with allium leaf miner? Just wondering whether you've tried covering them with mesh.
I thought I had allium leaf miner earlier this year. I'm still not sure whether it was, but I've covered with mesh this autumn in case. It's something I'm on the watch out for as I suffered from white rot for ages and then found a different rot-free area to grow alliums in, so especially keen to avoid further devastations!