Unless he was looking at you or aware of your presence, he can't jump the string at just 17 yards unless you're shooting a recurve or long bow--
Bright crimson blood could also mean muscle hit. And yes, you mightfind a few bubles in it.
Tail flickering like that though usually means he is pretty sick. Which would mean more of a liver/stomach/intestine hit. I think I'd go on that assumption mainly because it is real tough to be able to decipher blood color with wounds with great accuracy.
If you can not absolutely find blood, then I'd really suggest getting friends together andstart circling looking for blood. Start in close a few yards and gradually work your way out. If that doesn't work, then grid search.