This happens all to often and why we stress the availability to nest boxes in barns where farmers store hay.. from the Barn Owl Trust-
Stow Away! A rescued Barn Owl has just been delivered to us by the good folks from the RSPCA - found in the back of a lorry (truck) which has traveled all over the country! We will give it a health check & keep it with us in our large aviary, over the worst of the winter weather. The beautiful owl will be released back into the wild at a suitable site in the spring.
May 2011 Video from Bend Org