I didn't take the time to read all of Frank's comments, and I have no intention of trying to respond to him at length. I will address your original question.
Hogs, like many snakes, will ovulate when they have contact with a male. There are probably many physiological and environmental cues which bring this about, but the most basic one is physical contact with another snake, and the smell of another snake.
If you handled a male snake, and then handled your girl, or at any time housed her, even briefly, with another snake, male or female, you may have triggered one of these cues which caused her to ovulate. It is rare, but it does happen. When two hogs meet they "greet" eachother by jerking and rubbing against each other. This action alone may stimulate ovulation.
The fact that she laid the clutch 4 days after brumation is just a coincidence. She went into her prelay shed, and then you dropped her temps to levels that caused her to become physiologically inactive. When you warmed her up, she passed the eggs. If you had waited 10 days to brumate (hindsight being 20/20) she would have laid the infertile eggs before you could cool her.
I've had this happen twice. Once, I placed a 250 gram, virgin female in a display cage with four other girls at a reptile show, and about two months later she laid 18 slugs.
If anything, I think your experience shows how Frank, in his first comment, was wrong. It is precisely because the snake was so cool and inactive that it held the eggs over winter.
Your observations of snakes active in cool temps are corroborated by several others, but keep in mind a cage at 55 degrees in your house is not equal to 55 degree ambient temps outside. At 55 degrees the sun can still warm a basking snake, and the soil it's crawling on to normal operating temps.
Anyway, it's an interesting example of how stuff sometimes doesn't go the way you want it to.
