From the story it sounds like the parents were notified by the university one day after he'd last been in touch, so someone (be it a roommate or dorm staff) was checking in at least daily.
The story specifically says Sam's friend Charlie contacted campus security after Sam stopped responding to Charlie and Kayla (Sam's girlfriend). Campus security wouldn't have known to check in within a day if Sam's friends weren't on top of keeping in touch with him. (Put another way, I certainly would've rotted longer than that if this had happened to me in college-- lucked into having my own dorm room & had acquaintances but not any friends who would've gone out of their way like that.)