55 lbs is heavy enough. Did you get a pass-through and recover the arrow? Much as I hate to say it it sounds like a muscle hit to me and not the vital chest area. I know you know what you saw, but it's happened to me. I saw what I wanted to see but no dead deer. In fact, I watched the fletching disappear in the side of a deer once, and guess what? The video replay showed that the deer actually jumped the string and turned almost 90 degrees till the arrow got there. Maybe that's why my arrow didn't have even a hair on it much less blood.