Just saw this message. Tell him to continue normal dosage. He should NOT double dose any days to make up the missed days.
Chances are, nothing will happen. He would have needed to miss many more days than 2 in a row to have issues.
I have missed a dose here and there by accident and have been fine since. It's not the end of the world. Body responds just fine but tell him to try not to miss any more.
He should take regular from now. Please tell him NOT take the missed 2 pills in the same time to recover . This is writing in med instructions. Just tell him to be more carefull from now.