Okay we decided to go on a little over night camping trip and when we came home we discovered that the buff orpington was sitting on 4 eggs, two of hers and two from the black sex link. She did not want to move and stayed up there for hours even when the internal temperature of the coop was hitting 100. This was a frustration as at 22 weeks I couldn't believe she wanted to be broody. She had only been laying for a couple of weeks, but sure enough we would pull her out and she would head right back up there. Anyways the broodiness of her is for another thread.
The real update is that while all of this was going on we discovered a soft-shelled broken egg in the run. At the time that we discovered this I had all three birds in the run by forcing the buff to be down there as well. I didn't see who it came from, but my wife noticed the black australorp standing over it so assumed that is where it came from.
The real update is that it seems if we include the broken egg we had an egg total of 5 eggs in 2 days from 3 birds. Unless I had one that decided to crank out an extra egg I think that my mystery crower was indeed a hen. I will keep an eye out for more eggs and try to break the broodiness of the buff, and I will continue to be optimistic that I have all females.