Stealing and using a debit card is theft. By using your debit card, the thief at least committed petty theft. Depending on the amount of money debited, how it was used and where, it's possible for a thief to violate laws in multiple jurisdictions as well as federal law. All of this determines whether he can be prosecuted for a misdemeanor or felony and if it's a local or federal crime.
Reporting the theft to local law enforcement in a timely manner is essential to the ability to prosecute. If a friend took your card, used it and gave it back afterward, and you spent time deliberating whether or not to report it -- you may have a difficult time getting justice later. However, reporting a card stolen to your local police or sheriff's precinct immediately registers the crime with the police, who can then take action both to find it and to bring charges, even if you or a third party can't find or identify the thief.
When a card is lost or stolen, it's important to swiftly inform your bank. Not only will this protect you against further theft, but depending on the bank and state, it may protect you against loss from unauthorized use of your card. Just as importantly, your bank wants justice, too. Banks and credit unions work with law enforcement to identify spending patterns, locations and any transactions that cross the line into federal crimes. Your financial institution plays an integral role in gathering the evidence necessary to prosecute.
In most states, individuals don't get to press charges. Local prosecutors decide which cases they want to try. You may find that your stolen card plays a part in a larger case involving a serial thief or crime ring. However, if the amount was very small, the card recovered and your bank protected you against loss, it's possible a prosecutor will let it go. Despite your feelings, you may have little to no say in the matter.