> a guy Charles who makes two letters
So Charles at least knows the information on the cards. Are you essentially saying that there's no way for Alice or Bob to distinguish that information from 'background noise'? If so, that is not a great analogy other than to illustrate a historical & incorrect perspective. Which may have been what you were doing and if so is fine.
> measurement "chooses" one of the states in the measurement basis
Okay, say you 'do some entanglement of multiple particles stored in two separate tubes' where you know there is some kind of pattern in the entanglement. Is the issue that there is no way to know how to find that pattern without possessing both 'tubes'?