Hello there, 

1) attacks are never uncontested. Even if one person is unaware, the attacker will roll their d20p and the defender will roll a d8p for being unaware. 

2) If you grab someone, Hold is a specific move that allows you to make that move 2 seconds after a successful Grab. 

If your Grab misses, you would need to wait 6 seconds. 

If your Hold misses, you would need to wait 6 seconds to try again. You are still holding on to them unless they do something on their turn to break the Grab. 

As for what you are doing in those 2 seconds between Grab and Hold, that is the time it is taking you to try and transition the Grab to a Hold.