Unfortunately it doesn't sound like we'll ever know the answer now, but as Wolftrap suggested, I think it's far more likely this snake was sick & not the result of anything
you did or didn't do. I cannot understand how the employee was aware that this snake was "sick ever since it arrived at the store" & yet they sold it anyway ?That
is inexcusable! IF that snake had anything contagious (which I would personally NOT rule out!) all the others it was with were also exposed & may suffer the same fate
in time. I hopethat your new snake will be fine: you got off to an awfully rough start on this, & while it's good that you're getting a thermostat now too, I'm still very
uncomfortable with the way you are left in the dark as to what was wrong with the first snake. I doubt that it will be alright (honestly), & since the employee KNEW it to
be sick before it was sold, then it's HIGHLY unlikely that you did anything that contributed to it's condition. I'm sure we don't have to tell you to watch your new snake
for any symptoms similar to what the other one did... (I'm not necessarily suggesting it's IBD...it's possibly neurological damage due to someone's overly-
aggressive use of chemicals to kill mites, or some other cause...but I'd want to KNOW before I got another snake from them.)
By the way, did you check (both snakes) for mites? Do you know what they look like, etc??? Please check & keep checking.