Sorry to hear about your experiences, but it does happen sometimes. It sounds like you might have hit the one low in the brisket- that shot will cause a lot of bleeding and good blood trail at first, but will peter out after awhile. I hit a nice buck just like that about 5 years ago- never found him. If the arrow was low enough to miss the heart, it's going to hit mostly bone, gristle & some muscle. There's a good chance he'll survive a hit like that. Next time aim for the same spot, but just a little higher, especially if you're shooting from a treestand.

P.S. if you had hit him in the heart, he wouldn't be alive 2 minutes later, much less 1 hour.