Single trigger? Pull the lock out. Take the side screw out and pull the lock out,, nothing will break. Sometimes it's easier to have the side screw loose a few turns and give the screw a tap to get the lock started out of it's mortice.
TC used two different single triggers, one has a "fork" in the end of the cam that the lock sear arm fits between,, it probably just dropped out of the fork.
Clean and oil the lock while you have it out,, when you put it back in, just be sure to get the sear in the slot for it in the trigger cam.