Can't hook 'em!

[Billfish715]

While I was fluke fishing last week I dropped a few mystery fish after what seemed to be solid hook sets. I was able to keep tension on the fish with enough rod bend. I never raised the rod too high and was able to crank in line more than half way up. A couple of times the fish grabbed a 6" grub and other times they ate the legal fluke strip only to drop them on the way up. I'm guessing they were sea robins because there was no damage to the grubs or the strips. I had a couple of grubs pulled off as well. I sure thought the fish were hooked solid. They had enough time to settle on the bait before I hammered it home. I was using braid so there was no stretch. The fish were definitely on the trailer behind the jig and there was enough hook showing through the bait to allow for a good hook set. The only other idea that comes to mind is that the fish held onto the end of the strip or grub and never got to the hook. That's hard to believe because of how far up I was able to reel the fish in with a bent rod. Any ideas?