I still dont believe that he was confident that she's his Nupur b'coz if thats the case and still if he allowed her to go thn i would say he's not THE MAYANK Sharma I know.
As Mayank is the one who is who would get his Nupur back come what may. Even while she handed him the divorce paper he did'nt just leave her alone in that pain but made sure that he talks it out and convinces her.
Dont you remember
"Tum jitna bhi jagad lo, ladd lo ....end mein tum aogi tho mere paas hi ...aur tab thak main intezaar kar lunga"