shilsen
Adventurer
What ColonelHardisson said. Now that he's told you and deleted it, unless he starts pulling out and using information from the module in-game, it shouldn't be a problem.
If you're worried about his knowledge causing a problem, wait and see. Meta-knowledge isn't a problem with the right player. In my group we have a couple of people who take turns DM-ing (me included). Another person is DM-ing the RttToEE module. Since I spend a lot of time on these boards, I often run into information about the module, since everyone doesn't provide spoiler tags. My DM knows that I've known a lot of stuff before they occurred, but I never used the information, so it was never a problem.
Give your player the benefit of the doubt.
If you're worried about his knowledge causing a problem, wait and see. Meta-knowledge isn't a problem with the right player. In my group we have a couple of people who take turns DM-ing (me included). Another person is DM-ing the RttToEE module. Since I spend a lot of time on these boards, I often run into information about the module, since everyone doesn't provide spoiler tags. My DM knows that I've known a lot of stuff before they occurred, but I never used the information, so it was never a problem.
Give your player the benefit of the doubt.