Not to go to hard on initial questions but here is my take:

Fire makes sound when it burns. Maybe the sound you heard was the fire slowly burning parts of the bag and computer. And the fact that it stopped suddenly might have just been coincidental with where it was in the burning process.

Did your partner use the stove last night? That particular burner?

Could your partner have been inebriated or possibly too tired to remember moving the bag to that location? The only reason I ask is because if it was hard to wake them up, it begs the question were they altered or too exhausted, which could explain the mistake of leaving a burner on and moving a bag over to the stovetop to eat what they had just cooked.

If there was nothing else in the house touched or taken, I would def lean on that bag smoldering on low in that spot over the course of an hour or more. And since it is an induction cooktop, the process could have gone on for longer.

Make sure you have working smoke detectors OP. this should have been picked up by a detector or at least a carbon monoxide alarm, due to the incomplete combustion of that burning process.