If you lose your debit or credit card you should notify the bank or credit card company right away so they can stop your credit card or debit card from being used.
If you notify the bank about the lost or stolen credit or debit card and someone is able to make purchases on that card then you're protected from those unauthorized debit card or credit card charges.
But if you don't let the card issuer know about the lost or stolen credit card before it's used then you could still be liable for the unauthorized charges to your debit or credit card.
It's very important to report the lost or stolen debit or credit card immediately after you discover it's lost or stolen.