Sorry to hear two can't be found. We free range our flock and go running when stress calls are sounded, it really helps to get outside right away to give them support...
while the flock can be noisy at times the stress calls are the ones to be alert for. Once you know what they sound like, fast action can save your hen.
This is part of the risk we take with free ranging, however the hens wouldn't want it any other way, it is the way life is lived to the fullest.
It is possible that they got away. We had a case where a fox tried 3 times to catch one of the flock. Feathers were spread enough that you would think she killed one for sure. We found one roo 250 yards from the back yard, upset, confused, but ok and another hen under a spruce tree near by. Maybe looking some more might be worth it... Good Luck.
bigzio