Certainly sounds like something has given them a fright. Could be fox, or even a dog.
Lets hope she has gone to ground and appears tomorrow. If you can, get up early - as if she is out and about she stands more chance of being taken early tomorrow morning when she reappears. Just nip out and take a look at her usual places, if you find her you'll be glad you did, and you can put her somewhere safe until a decent 'get up' hour.
In the past my birds have been lost to fox during the day, and just the once I lost chicks to a stoat.
Not sure if an owl would take, I don't think they hunt anything that large, keeping to nothing larger than voles, mice and the like.
Let us know how you get on.
Best wishes.