I dont think you took and ill advised shot, your shot selection from your description was good. You said you hit her low but do you know how low? I have seen hits where the arrow (or gun) went through the bottom of the chest but below the heart and lungs. These hits have caused a ton of bleeding initially and then done just what you describe, finally just dissapeared after the deer went quite some distance, and I will say I have never found one of these deer. I think my tracking skills are prettygood, so that makes me think they might just survive.?.? Typically the bottom of the chest area has some very dark grey hair before it turns white towards the belly, what about the hair for your hit?