Hi, I also feed f/t but if my snake refuses to eat it - I throw it out since you are not supposed to re-offer food until the next feeding which is a week away and I wouldn't recommend re-freezing them.
I don't think there's anything wrong with re-freezing once...just keep in mind that each time you freeze it, you increase your chances of having it "pop" after it's been thawed out. And that, my friend, is a disgusting event!
Just remember, I think when they start to thaw they begin to decompose and spoil. The longer it's been thawed, the less and less I'd want to refreeze it.