I'm thinking a good reason that he hasn't missed a meal is because a fuzzy for an 8 month old (and I hope you're talking rat) is teeny!! I would definitely bump him up in size, if you have that option (I understand that since you're snake sitting you might not have that option open to you!) At the very least you could give him a couple of fuzzy's per feeding or at least feed every 5 days. When the owner returns, you might suggest that the prey size needs to be larger!
Also, sounds fine that the snake hasn't shed- they'll know when