Purchases are often succeed or fail for arbitrary reasons.
Perhaps the customer couldn't find a parking place they liked and moved on. Or they hated the clerk with the untucked shirt. Or they liked talking to the pretty girl at the counter. Or your store is next to their favorite lunch spot and they passed through on their way to their car. Or they expected a cheap commodity and found rare quality instead.
You can only worry about the factors you can control, and mitigate the risk of the things you can't. Focus your efforts.