D&D4 Wiki
No gambit is wasted
warlord attack 3

Trigger: an ally misses every target with an encounter or daily attack

Target: one creature targeted by the triggering ally's attack

Attack: Strength vs. AC

Hit: "2[W] + Strength modifier damage. The triggering ally's attack is not expended."
Insightful Presence: "The triggering ally gains a bonus to his or her next attack roll against the target before the end of your next turn. The bonus is equal to your Wisdom or Charisma modifier."[MP2:86]

No gambit is wasted is an encounter power available to warlords at 3rd level.