If you have lost your credit card or it has been stolen or mispalced you are required to apply for duplicate credit card along with blocking the earlier card.
==How to Apply for Duplicate Credit Card==
1. If you are unsure whether the Credit card is lost permanently or stolen, you should immediately contact the credit card department of the bank who had issued the credit card to get it blocked permanently, you can also block it temporarily if you think the credit card is only missing and you can recover it later. All major Indian banks like ICICI, HDFC, AXIS, SBI now have 24/7 phone support so you can easily block your credit card. Do note that you may have to pay some blocking/unblocking fees for the credit card.
2. While calling the Bank helpline numbers, do ask them about last transaction, if you think there are some unauthorized transactions being taken place, then you are required to make an official police complaint so the credit card company and bank can investigate the transactions. If there are no unauthorzed transactions were taken place, you can avoid the police complaint to save time and just block your card and ask for Duplicate credit card from the bank.
3. Normally issuing new card cost Rs 200-500 depending on the bank and type of card and it takes about 4 weeks to reach you (unless you are in metro cities). The new credit card number will have the same Credit card number and expiry but different CVV number. From the moment of reissuing new card, your old card will become useless so even if you find it later, cut it in multiple parts with a scissor and throw it away (so others can not guess your credit card number and expiry.