I shot a hog with a crossbow in the shoulder an he bled 1time about 30 yards and never retrieved it nor my arrow. Looked for the thing for about and hour though short pines that are about 18ft tall an it backs up to a deep swamp
You didn't give an indication as to how large the hog was. But if he was a really large boar, there's a chance that you simply gave him a minor wound. This video gives a good representation as to what bow hunters face when shooting a really big boar in his shield area. The best place on a big boar to place an arrow is when he is quartering away, and you stick him just behind the shield angling forward.
I hunted bear in Maine several years ago with a guy that guides at this place. They show, in this video, an interesting experiment on an actual large boar's shield and a quality broadhead shot into it. I found it pretty interesting.
I became a "believer" when I killed a huge Georgia boar years ago with a Marlin .44mag Carbine shooting 270gr Gold Dot loads. The bullet labeled #2 here was dug out of that huge boar's shield (onside shield) after a direct center shoulder hit. The interesting factoid in that circumstance is that this shot never got through the onside shield at 45 yards. The "wound" never even bled. (Pic attached) For the record, #1 was dug out of that boar's neck, 2" from his ear. #2 was fired as the boar was getting back on his feet.
I saw that video several years ago. He was shooting a thunderhead broadheads, they ain't no joke either. Heavy arrows make the difference. Their tuff as the come.