There is something that needs to be learned here so you don't do it again....if it was just a "slight hinge" (a subjextive and debatable phrase pending on ones own opinion and experience level)as you said then your design was probably too narrow and not wide enough to support the load(as long as the wood was dry)...so was you wood dry? What were the specific dimensions? How much weight were you pulling(never pull past intended target weight) ...you obviously did something wrong for it to fret at only 15"..and learning why and learning from the failure will help you in the future and to not repeat that mistake
I'll move on. Dissapointing, yes, but its part of the learning process I guess. Hickory isn't exactly a rare or exotic wood and I've got a few other staves I can start on.
Not sure if these questions are rhetorical but I'm going to answer them anyway.
It was a legit hinge, didn't see it during floor tillering but started to work it out after I braced it. I should have fixed it completly right then but it looked 'better', but I continued on the other limb and getting some of the other problems and drew it a little further to 12, then 15 observing how the other limb was stiff (which also would have helped in chysalling), not paying much attention to the hinge, probably my biggest mistake there.
It was 2 inches wide most of the limb tapering to 3/8" tips and a 1" bendy handle, 50" long. Doable AFAIK, but without the hinge. Its been seasoning 4.5 months. About 1/2 of that in 'shaped' form. Never put it on the scale but it wasn't pulling really heavy or overstessed due to draw weight.
Just my complacency in tillering.
Moving on to to the next staves now. Thanks for the help guys!