Eatting half?

[Bogertophis]

It's still in the food bag it came in, and that's how people have told me explicitly to do so.

Doesn't matter what bag it's in, and we're advising you to the contrary. Properly thawed frozen rodents do not fall apart this way...only when they're spoiled & gross.
Remember that the rodents you're thawing are whole animals...their guts (ie. GI tract) are FULL of bacteria, which are all too happy to proliferate the longer they're at
room temperature. Take a cue from human food safety rules: thaw meat in the refrigerator (the slower way) OR thaw in cold water (the fast way)...& like I said before,
that's for OUR food, & it's being cooked, which destroys bacteria...our snakes are eating it raw, & very few are carrion eaters. Your snake was sadly desperate enough
to try to eat anyway, & this could prove to be a health issue for your pet.