Like I said, I would wait for the experts to weigh in. Pet stores are NOTORIOUS for giving bad advice.
A hatchling snake will eat until it kills itself if you let it. It trying to eat your finger means nothing more than your finger smelled like mouse.
In all likely hood, it regurged because the rat pink was too large, not because it tasted different.
Which is why you should follow a feeding plan. If you snake has another regurge, it could very well be it's last.
I don't claim to be an expert, BUT I am a trained biologist who happens to have 9 snakes (new world and old world). I have never had a snake regurgitate, mainly because I follow a feeding plan.
That is all I will say about it.
Good Luck,
~Beau