Unfortunately you don't know. I once shot 16 rabbits out of my garden before I got the last one that was eating my beans as they sprouted. Not all 16 were eating the beans as they sprouted, I had no way to know if the rabbits I shot were actually eating the beans but at least some were because it stopped happening.
I once had a skunk go through a pet door into my garage where the dogs slept at night. The skunk sprayed and got away. I trapped seven skunks in that area the next couple or weeks but I don't know if I ever got the one that actually sprayed. It was skunk mating season and the male skunks were on the prowl.
I once suspected I had a raccoon hanging around the chicken coop so I set a trap. I got a possum the first night. I set the trap again, and got a possum the next night. I set the trap again and got a raccoon. The fourth night I didn't get anything.
All these critters were permanently removed. They could not come back. I'm all in favor of permanently removing predators that are hunting my property. That certainly reduced predator pressure. But I don't consider it a permanent solution. Even if you get the one that is the current problem, if there is one there are more. It's not like any of these are going extinct. There ae new ones being born and setting out to look for their hunting grounds. The only really effective protection is barriers. Good barriers work whether you are there with a gun or have a trap set.
I would absolutely reset that trap. Are you sure a raccoon didn't get that chicken and the fox was just an unlucky passer by? Congratulations on getting that fox too, they are not easy.
I would also keep the chickens locked up for a while, more like a month than a week. If it were something other than that fox, make sure it knows there is not an easy meal just waiting for it.