I haven't rooted any leaf cuttings myself, but my first bet would be that the heat in the sealed bag got much too high and that's what killed things off. The fact that the leaf died so quickly really points to overheating, IMO. If you try it again, I suggest putting them close under fluorescent lights, which put out moderate light but very little heat. And I wouldn't seal the bag too tightly... they still have to breathe.
-Don

I do it any time of year. As long as you have decent lighting over it, it can sprout. Blacked material is normal, even if the basal part does sprout. Give it more time to indicate whether it is tryly dead or not.

What I like doing is embedding the basal part in living LFS, exposed to the air, and kept wet. It can take several weeks before you see anything sprout.

This method also works:

{{gwi:555544}}

Is that plain, distilled water you've immersed the cuttings in? Any hormone, etc. added to it? Is it necessary to leave a bubble of air at the top for breathing or can the entire VFT cutting be submerged? I might try make another go after the plant heals... what is a reasonable length of time to allow it to recover?

There is an AWESOME website with lots and lots of FAQs, as well as some really specific stuff:

http://www.sarracenia.com/faq.html

It's nearly as addictive as this one.

Yeah, I've been through Barry's site already but unfortunately it seemed like my questions were a little more specific (although major props to him for undertaking such a project--some parts are pretty funny to read too, like the section on protecting your plants from pests). I was severely addicted to his FAQ for the better part of a week or so ;p.

Distilled or RO or deionized would be the best, as it is the cleanest. I think that these were actually done in rain water. No hormone used. No bubble was intended. The D. binata take ~3 weeks to sprout. VFT's take longer. The important part is the basal (white) part of the leaf. Personally, I find that VFT leaves do best when the basal part of the leaf is embedded in live LFS, exsposed to the air, right at a window sill.