Thanks for all the feedback. I definately won't be charging any suspect cells. It might be cool to see what happens...but for $20, I'd just assume trash it an buy a new brick. I've got LiFePo4 cells for misc. tasks...so I don't really have a need for recovered LiPo that may or may not be prone to further failure.
After some research, I've found that in Li-Ion cells with liquid electrolytes, the separator is designed to melt during a thermal runaway...effectively nullifying it's pore structure and shutting the battery down. Does anyone know if the separators in polymer electrolyte batteries are designed to perform the same shutdown?
If so, then I could buy that as a mechanism for failure: something finally gave way internally, the battery shorted and separator served it's shutdown function. That would explain the 0v / yet seemingly conductive outcome as well.
Though a bit dated, some good info on battery separators was found here: http://tinhoahoc.com/Battery/cr020738u.pdf