a newcomer's query - HE folds effecting winning chances

[clay1m]

I have a question along the same lines as the one posed about AK vs 77, but I think it would come up more often. For example say that I take a flop with two other players in a ten handed game of limit Holdem. My hand is 2 cards of the same suit. The flop gives me a flush draw. The mathematics you can find in any book on poker theory now tells me that since I have nine outs with 2 cards to come I have approx 35% chance of drawing to my flush (assuming my opponents have none of my suit) It seems to me that this is very unlikely because 7 players were dealt cards that were folded preflop. Surely some of those cards that are now in the muck are my suit. In fact it would be a remote possibility that all of the cards either in the muck or in the hands of my opponents are not of my suit. So if I know that I must make my flush to win and I continue playing based on the fact that the pot is offering me correct odds for a 35% chance of winning could this be an error?