This seems to contradict the rules.
A wounded Posse can:
* Retain the [!] benefit of the placement spot it occupies.
So if the Attacker loses the duel and is wounded, he does not get to benefit from an Instant spot in any way?
Edit: it's clarified in the FAQ on the bottom of the box that attacker must win to benefit from the spot. Leaving this here for others who stumble across this as well.