Head on shots are risky because the vitals are not gonna be where you expect them to be. You can easily shoot in front of them or into the opposite arm. Or you can hit the arm bones like you did. If the arm was forward at the time you shot, thenyou could easily have hit in front of the lungs. Over the spine would also make the smack noise because of the bones above the vertebrae.

If you found any blood then you should know what you hit. You know how it goes: bright bubbles is lung, plain blood means... etc.

I've had a few bad experiences shooting animals while they were quartering towards me. I figured out that it's way more satisfying just letting them walk if they don't give be a perfect shot angle.

And 25 yards is a pretty long shot. Yeah, I know that people shoot deer at 40+ yards but my shots are taken from point blank to 20 yards. Rarely do I take longer shots than that. If I ever took a quartering towards shot, it couldn't be more than 30 degrees quartering towards me and would need to be much closer than 10 yards.

It's always best to wait for the perfect broadside or quartering away shot. You never really know what you are gonna hit when it's quatering towards you.