I would like to explain to the student why this is happening
Could be a number of reasons but the usual one I come across is when the recording device has failed to finalise the file. This could be due to a DAW crashing before recording is comlpleted, or a flash card is removed from a device or device powered down before file header has been written.
Best ask him how he produced the file.
Recovering the file, as has been stated, is easily done with something like Audacity (easiest becasue it's free). Import RAW file, it will ask you to fill in header values - bit depth sample rate, channel count. Then it's just a question of saving that file.
I must agree with Dan though. If this is submtited work, the student should have double checked their work.
I'm All Ears.