Wow, I do believe it is possible they have flashbacks. I have 5 Dogs total, 3 are rescues. The oldest one is an approxiately 7 years old pug, she was nearly bred to death/abused by the previous owner who dumped her in a dog park i was at with my other pugs . Every now and then she would flinch when Women bends down to pet.
So, if it is possible she took a disliking to women, i believe that All dogs have trigger objects. Triggers can be Things/persons/Smells/feeling. As the others have said, i would take him to a vet to just make sure. I am sorry to hear that the coyotes took the other dog.
I hope everything is allright with you and your dog.