Relax a few missed feedings wont hurt him much, they can go months without eating, if he has been eating for your prior, then it is his stubbornness most likely. taking him back to the pet store for a week, uhm,.... i would highly advise not to that will add a lot more stress and chances his hunger strike will last even longer, then the quarantine time once he returns, if it was a few months then i would consider being worried. not after a few meals. especially since he is a new animal, i still got one snake i got back in February that still has not eaten for me, but ate consistantlly for the breeder.