I've lost hogs with Grizzlies, and pretty much every other broad head at one time. It is shot placement and on bigger hogs it has to be tight. Ideally, I want a pass thru shot, blood squirting out both sides. The fat tends to close the blood trail down after a few yards without one, or it just fills the chest cavity after a few yards. The only time I've dropped one in it's tracks was with a shot in the forehead.
Like said above, if they run off into water or a swamp I'd stay right on top of them and try to stick them some more. If they are going off into some thick cane and thorns, no matter how much blood has been laid down, I'd give them at least an hour and that is no guarantee. Don't even go in the thick brush to look for blood, a lot of times they will just go in about 20 yds and lay down. If you go in checking for blood they will go another 20 yds, and etc,etc,.
They can be frustrating, but to me they are the ultimate Bow hunting stalk animal. Good luck