I've had this happen, too, but mainly with stocked fish in NC and VA. I think the shape of my strike indicator (I use football-shaped indicators) might remind of them of the trout chow from the hatchery.
Or it just could be something different looking that looks worth taking a bite out of. I try not to give trout too much credit for reasoning.
However, in your case, and again thinking from the fish's perspective, a relatively big, pear-shaped object would look like a beetle floating in the current to me. Especially considering that, with the bright sky as a backdrop, the orange color might not be so evident to the fish...he might just see a dark silhouette that's roughly the size and shape of a beetle.
I like fishing with nymphs, too, but if "the biggest fish in the given hole" just busted my strike indicator, I might be inclined to have a seat on the nearest big rock, tie on a nice foam beetle pattern about the same size as my strike indicator, and puff on a cigar for about 10 or 15 minutes. From a safe distance, see if you can see the fish on his lie while you're waiting. Let everything calm back down, then float your beetle down the same seam where you got that strike.
One of my favorite things to do is to find a fish like that, and then to change my strategy/presentation/fly until I figure out how to get him to take.
Good luck! Wish I was in Montana having trout bust up my strike indicators...if you're going to have a problem, that's the kind to have!