This theroy calls to mind the question: Can a Windrunner suck in stormlight leaking from a person? If the only reason they can draw it in is because it leaks, gratz, you're at least partially right. Unfortunately, I don't think that's it. I think it's a bit of a stretch to assume rocks hold stormlight, considering a number of things. Most important of them all is the reason you can't soulcast gems. If you could, you'd have limitless power, creating infinite wells of it by turning air to gems. Likewise, if this were true, you'd just soulcast a whole bunch of rocks, and somebody who can get it out would do so, gaining limitless power. Sorry, but I simply don't agree.