I personally feel it isn't your responsibility to take your time, energy and gas to track down the chicken owners. If it were me I would quarantine and add to the flock if I wanted them. I would only quarantine them in case the owners came to me in a reasonable time to find them, it is their responsibility to keep track of their birds and track them down if they want them and keep them from getting out if they want to keep them. The quarantine in this case would just be to keep them separate in case the owners came back b/c if I understand correctly they have already been exposed to your birds.
Agreed.