If a monster rolls an attack that misses but it generates enough surges for threat, does the OL get the threat?

Surges only count if the attack hits.

From Descent rules: "If the attacker has not rolled a miss result, it is possible for the attacker to modify the rolled range and damage through one or more of the methods described below..." One of the methods described below is the OL trading in two surges for a threat.

I think its also covered in the latest FAQ