Yoshereeshay, you're taking a big gamble by planning to snipe an item that's been put up with the "Buy It Now" option. What that option offers is the opportunity to buy the item for a stated fixed amount on a first-come-first-served basis. When the item is purchased under "Buy It Now" the auction is closed and the item goes to the person who excercised the option. You might have had a much higher bid slated under Auction Sniper, but that bid was never placed and so didn't count.
If you want to snipe something that's on "Buy It Now" and you think you can snipe it successfully for less than the set price stated, put a minimum bid on it. That "kills" the "Buy It Now" option and you can go ahead with planning a snipe without worrying that someone will buy the item out from under you before the auction closes.
Good Luck!