I have several things to offer, or say. First off it must be the changing of the times that you are fly fishing but 'not much of a dry fly guy'. Please remember that I am a bit old school here but back in the day that's how you started; fishing dry flies. You did that because learning how to fish nymphs dead drift with no sort of indicator was very hard indeed. The use of streamers also took a lot of understanding of things you could not see on the surface and thus we fished the dry to learn casting and control. I don't want to start an indicator bashing argument here but I have always suspected that their use would lead people away from the true heart & soul of fly fishing which has always been the art of fishing the Dry. If that's what had led you astray then welcome to fly fishing. If not please excuse my remark entirely.
Silver creek has alluded to subsurface feeding being what you thought were rise forms. Over the years I have experienced the same circumstances that you describe. In all likelihood the fish you saw chasing the fly were smaller trout not old experienced giants. Small fish often behave in ways I could never begin to explain but the fact that they would pursue the fly suggests that they were eating an emerging aquatic insect and perhaps one that could swim pretty well. Such things as this are what keep it interesting.
If this happens again you might try what I had good success on the spring creeks of Pennsylvania with. Find or tie a Blue Quill in size 20. Fish these on 7X fluorocarbon leader and be sure to use the Orvis loop knot to attach the fly. The knot keeps you from busting that 7X tippet. I haven't run across many trout in a spring who will not take that little fly and I fished in quite a few.
If you work on your dry fishing you will gain a great deal of pleasure from it. Of all the ways I've fly fished it is the most relaxing, the most graceful form of the sport.