I'm of the opinion that snakes cannot cough. I agree that is why RI's are deadly. If they could cough they would do so to expel the excess mucus. I guess it could have been a dry heave.
As far as bedding goes try newsprint. It may not look the best, but there is no chance of it being swallowed during a feed and is super easy come cleaning time. You just toss it.:gj: