Skirmish Events

[Gerontius]

This came up in the last game I played. I'm not sure what to make of it, it seems like it should be illegal but I can't find 
anything in the rules that wouldn't allow it.
He had played a Dunlending with a War Club, no other minions. I wanted to save my Axe of Erebor, so I assigned it to Aragorn, GaP. I played a Battle to the Last, and used Gorn's effect to kill the dunlending. The way I reasoned it was:

The event says: "Spot a Dwarf." I spotted Gimli, paying the cost of the action. Because Gimli was not assigned to a skirmish, the strength bonus had no effect. Aragorn used his effect.
My opponent argued that I couldn't even play the event because I had no dwarf in any skirmish.
Who is right, and why?
Thanks again!

[Elgar]

You were.  You can play a card as long as you meet all requirements and pay all costs.  Since you can spot a dwarf you can play that event.

[Vroengard]

yap, right.

[Kralik]

Nice trick.

[Gil-Estel]

this might be a good moment for: all cards do exactly what they say . Spot a dwarf, check, make him strenght +, check, Gorn kicks in: double check.

[jdizzy001]

I triple check that!  You were right Took, very clever use of the GaP...