I did the same thing. After thawing the rat fuzzy out, I take a hair dryer to it and make sure I'm blowing it in the direction of her enclosure to trigger that feeding response and then I spend a little more time on the head to give her a solid target. After that, I double check the temperatures of the rat and then feed it to her. She took to frozen thawed immediately on the first try. She was already on live fuzzy rats when I got her though so I never had to deal with switching from mice to rats.