[IanCal]

It's not a dumb question, that's what we should start by assuming because it makes a lot more sense. This is referred to as "local hidden variables".

Bell's theorem (http://en.wikipedia.org/wiki/Bell's_theorem) and the tests around it show this to be false, things just don't act like there's a variable we simply don't know.

[HCIdivision17]

That is exactly the experiment I couldn't remember the name of and tried to ramble my way around it via another route.

This is the clearest way to understand that it must be truly random and not just hidden ignorance of state, and has been tested to a remarkable degree of accuracy.