The Strongheart Tattoo DDI has the benefit:
When you spend a healing surge, you regain extra hit points equal to the number of healing surges you have spent since your last extended rest.
Will this apply, e.g. when you've lost healing surge(s) as a result of failures in a Skill Challenge ?
One side of our discussion is... I have X healing surges, so my StrongheartTattoo` bonus is simply equal to ... " X - ( current number of healing surges )" no matter how I've "spent" them.
The other side is the ones you've lost have not actually been "spent".