I HOPE I'm wrong here, but my hunch is that it also regurgitated in the store & they didn't want to deal with it- beware of "free snakes". I HOPE there's nothing else living in your snake rack? And that this snake has been well-quarantined by you, as it's most likely sick & this site might come in handy, if you don't already have a nearby trusted herp-vet:
https://arav.site-ym.com/search/custom.asp?id=3661
As I said, I HOPE I'm wrong but an underweight snake that's not regurgitating because of handling & husbandry errors (temps. warm enough, privacy, etc) may be a seriously ill (& contagiously so) snake. Pay close attention to this snake- is there any mid-body swelling? Any neurological issues? (does the snake's balance seem off?) Crypto & other bad things come to my mind-![]()