The Visa Thing really isn't where intelligence belongs actually. See, when traveling abroad a Passport is often all anyone needs. So, if the gentlemen in question presented his Passport as reason to enter the USA it might not have been questioned. I don't know the exact State Department requirements for folks traveling from that part of the world, but, a Student Visa gives people permission to be in the USA for an extended period of time. A Passport usually gets a person a short period of time, up to three months or so, to travel in the USA.

Customs would have to know they needed to look at a Student Visa and if the Passport was still valid I am not sure that student could be stopped anyway. Again, that is specific to any travel restrictions on that part of the world.