Whether someothing is a crime depends in large part on intent (a/k/a "mens rea"). If the bartender did not intend to steal from you in some fashion--such as by knowingly collaborating with your friend to allow your friend to use your card, or by accepting payment for giving your card to a different person--there is no crime. Merely negligently or carelessly giving your card to another person without a criminal intent does not incur criminal liability. If the bartender was unreasonably careless (negligent) in giving the card to your friend, there might be civil liability against him--i.e. you could sue for damages, though if the damages are only  $17.50, that's not worth suing over.If anyone acted criminally, it might be your friend--knowingly using your credit card to buy alcohal w/out your permission--though if he intended to repay or thought you would authorize the transaction or was buying the alcohoal, even mistakenly, for you, there's a good chance his behavior, too, was negligent at worst.If the owner overcharged you (and you can prove it), he needs to return the money and you may bring legal action if necessary.