I hadn't really thought about the issues of hair in the digestive tract before this thread. I knew hair didn't digest, and I often see it in the faeces of my snakes that eat an all rodent diet and just assumed that in a healthy animal it just passes through. It's interesting to think of their diets in the wild, and as mentioned above garters have no means to kill rodents. I haven't seen a garter constrict yet anyhow.

As for the small garter with the care fresh, could you try bathing it in warm water to encourage it to defecate and see if it passes it?