It’s time for a double feature! DnD 4e and Pathfinder together!
Pathfinder First
Hostile Negotiations:Feat-You may use an intimidate check in place of a diplomacy check. Your DM may judge that you can not repeatedly use this feat several times in one conversation. If you fail a diplomacy check with an intimidate check, the result is as if you had failed an intimidate check.
Now time for DnD 4e
Hostile Negotiations
Skill Power (Intimidate) -Level 2
Encounter
Effect:You may substitute an intimidate check for a diplomacy check. If you fail the check, the results are as if you failed an intimidate check.
Throat Punch Games 
I think that because you are using intimidate as a diplomacy check the failed result should be as per a failed diplomacy check not intimidate.