Do you mind sharing your arrow weight? Also, good on you for the want to change something to help.
You are also spot on to assume a huge mechanical wouldn't have penetrated as far. That is 100% correct.
Any single hole high lung shots, with any BH, won't always cause good blood trails. Even with something like the grim reaper carni-four. The blood is mostly just filling up inside the cavity. Typical to have just drops until the lungs are full & it starts coming out the nose & mouth. If they are running that can be a good distance.
The best blood trails I get are one's that are more into the V & two holes. Doesn't matter the BH. I wouldn't recommend hugging tight into the shoulder vs behind the crease, unless you have the arrow weight made for it. 55lbs is more than enough if the arrow weight is up. Trajectory will decline, but you'd be more forgiving, quieter, more likely 2 holes on shots like the one you encountered. Even if you where to go the stupid extreme heavy & pay really close attention to ranging prior to the shot, you'd be full proof out to 40 yards easy. I'm not saying you need to go stupid heavy, but guessing heavier would help.
Imo, a heavy arrow, good single bevel, & punched through the V produces a better blood trail than a light weight arrow with a huge expandable, hit behind the crease. High or low. Not to mention they die faster.
Going heavy has given me the highest recovery rate over high poundage, speed, or BH selection.
I know a lot of people hate heavy, but it has a lot of killing benefits as long as you know the limitations & pay extra attention to ranging yardage.
Fact is, if you were shooting heavy & that single bevel you would be eating that deer.