My fault I'm afraid, but a similar tale. In the open area I only had netting for the roof of the area as I figured if the quail took off startled straight up, they would not be hurt.
Unfortunately, during the night/early morning the owl must have seen them moving and got through it, only to not see the entry/exit point once in side.

I swear I keep doing things with the best intentions and something happens and I have to start again. Its a lesson in frustration and wasted time, but a valuable lesson nonetheless :-P