It should be no problem if Android Device Manager was left enabled in the Security settings.
But first off, usually with a pattern lock on Samsungs, if he keeps trying enough times he will be given a screen to either enter a backup pin number OR a username and password (I think that's how it's worded). Basically it's asking to enter his Google email address and password.
If that doesn't work, log in to his Google email / account on a pc, go to Device Manager which will find the phone on a map if it's on, and select "Lock" which lets you lock! the phone and enter a new pin number, so overriding the old pattern lock.
Good luck.
www.Google.com/android/devicemanager
From my SM-N9005 Note 3 on Tapatalk