I've read a couple of articles (one on kingsnake.com) that said to get some snakes to start eating f/t rodents that it sometimes helps to thaw and refreeze than thaw again (this makes the scent more appealing to a snake) But I don't think it would be the same thing as thawing and letting it sit around for a few hours than refreezing.
I have defrosted a rodent left it in my balls enclosure late at night and if it's still there a few hours later I would than try it on my boa who eats during daytime hours. If he doesn't take it right away than I throw it out.
I think it's amusing that people hate throwing out a rat because their snake wasn't hungry but have no problems throwing out their own half eaten meals. (come on we've all done it without giving it a second thought)
Ginnette