about 1-2 years ago i bought a 2nd hand gopro hero 2 that also wouldnt start anymore,
the guy didnt do anything specific with it, it just randomly stopped working,
if i remember right the light did turn on if he connected a charger/usb cable but never managed to turn it on,
i looked on the internet and found some people that had this problem and fixed it by putting the gopro (in a sealed bag) in the freezer for a while and after taking it out turn on the gopro and it would work, then directly charge it and it should be in working condition again...
i hope its not too late and all, would be a waste, look it up on the interwebs..