Alice, if the tech was using the lighter at the hammer shank, it was probably to heat the glue. I don't know if they still use horse-hide glue or not, but it was common fairly recently. Wood doesn't get more flexible with heat alone; it takes humidity to do that. So maybe the tech was heating the glue to loosen the shank so he could rotate it to a better position. But I bet you are right about what he was trying to fix. I sure wouldn't want a tech in my piano with a lighter, though!