Look for the following clues: Was the case split? Was the primer pierced?
If neither of these effects is visible, and the case is sooty from the neck back, then it was a squib load, the case failed to expand, and the rifle is possibly* OK. And if the shooter did not even look at the case, then for heaven's sakes send him on a course to acquire some basic knowledge, in the interest of safety.
Patrick
*That was a "possibly", not a guarantee! It must be checked over.