Exactly what Edshez said:
You never count what a player "might" be holding in any of your equations. Outs are outs - If you haven't seen any cards then they are still your outs. If cards are accidentally exposed in "live" games and any of them were your outs, then you would not count them any in calculations.

However,
If you know the players you are playing against - You can use that to your advantage.

If there are a lot of large bets in a hand and you and another person are simply cold calling - You might be right to assume you are both on a flush draw and if you have a low flush draw it migh be wise to get out of the hand for fear that if your flush hits you are still losing to a higher flush.
Pay attention to how your opponents play and it can help you out in tricky situations!