Regurgitation?

[Bogertophis]

I watched him while the rat was still alive then left him alone to swallow in peace once I was sure it was dead. I checked in briefly maybe half an hour later to confirm that he'd finished and he seemed fine. It's the first time I've fed him live but I know that's what he was given before I got him.

I've had Simon for 4 years and two other ball pythons for 3 years. Their thermostats are set to turn off at 98F and as far as I know there haven't been any power outages. I didn't notice a smell from the dead rat but I don't have a great sense of smell to begin with.

You need to check -immediately!- what the temps are in your snakes' enclosures where the heat is located- specifically, INSIDE the enclosure, under a warm-side hide or wherever the temps. are the highest. 98* is TOO HOT. Many snakes (BPs especially) get burned when in contact with surface temps over 90*- seemingly they don't realize the harm until it's too late, but in your case, your snake MIGHT have realized it's too hot & therefore avoided the warm areas...but then was too chilly to digest well- hence the regurgitation.

Note- you cannot rely on what a t-stat is set to- you need to double check what the actual temps are INSIDE the enclosure where the snake can touch (underneath substrate also, because they often push it aside) with an IR/laser temp gun or other accurate thermometer.

This time of year, most of us use A/C for our own comfort, so it's essential that you adjust the temps. provided for all your snakes to be sure they have the proper & SAFE range of warmth. BPs need about 78* lowest & 88-90* warmest, with matching hides on each side so they aren't "forced" to choose their sense of security over the temperatures they require to digest & function.

The only way a regurgitated rat might not smell really gross is if it was left to dehydrate under the warmest part of the cage, but it takes days to become that dry. I know of no one that cannot smell a regurgitated rodent, so perhaps this actually is funky stool? Stool doesn't smell good either but a regurge is THE worst, & either way, it's not a good thing (judging from the appearance shown in your photo).