New Note 7 Rebooted and Erased All Data on First Time Insert of SIM card. Why?
This appears to be an undocumented feature of Note 7 as per this XDA thread  Samsung factory restore after inserting SIM for the first time on GN7 by ninja0n3
OP here faced the same problem and reproduced the chat transcript with Samsung help . Extracts:

Veronica (Samsung): I would like to inform you that, It will be reset to Factory settings, when you insert sim on the phone.
J.B.(OP): every time?
J.B.: so I go to another country, and change the sim card so I can get cell and it will delete all my data?
Veronica: No, it will delete the data when the sim is inserted for the first time and when you change the carrier on the phone.
J.B.: So if I put a sim card from a different carrier on the phone while I am abroad, will this reset the phone?
Veronica: Yes, you need to backup the phone before using another sim on the phone.
Veronica: I am sorry for that. As you insert the sim on the phone it will be restored to factory defaults to get the phone locked to that carrier.
J.B.: Is the carrier informed of this process?
Veronica: No, this has been started with the Note 7 phone. As it comes with Marsh Mallow OS in it.

(Emphasis supplied )
This does not fully explain OP's experience, for instance, reset didn't happen when co- worker's SIM was inserted ( unless first  time refers to the phone ), so gaps would need to be filled by Samsung / Carrier
All Hail Samsung (sorry, couldn't resist that)