1st: Look for it (them) again
2nd: If fails, call your bank hot lines to block it as soon as possible.
3rd: Make Lost Paper at the nearest police station
4th: Check to the nearest branch of your bank that issued your card to make sure that it's blocked
5th: Apply for the substitute card. Usually it takes your ID card, the Lost Paper, and your saving book (or latest statement)
Here is my experience when I lost four cards from 3 banks, one government bank, one private bank, and a sharia bank. (clue: they are the largest one, I suppose). I lost them in my hometown, the accounts are all opened in different cities than my hometown, and I didn't have the saving books with me (they sit well in my cupboard in my boarding room). I didn't call the hotlines and already make a lost paper at the police station.
Supply your ID and your account number, and your lost card is blocked. They can help substitute my card if only I had my saving book. But then, when I requested to replace the card, the bank in jogja needed to get approval from the branch where I opened the main account first, and it takes approximately an hour to complete. Yet, the new card takes another two to activate.
They ask you to call their hotline and follow the procedure (because my account is not theirs). It takes almost half an hour because the line is always busy and after that the officer keep me sitting by promoting their products as if I didn't know them yet. They can help substitute my card if only I had my saving book. Yet the block will only last for five workdays. But then, the replacement card completed in under half an hour and ready to use.
The cards (two accounts here) are blocked in no time as you supply the account number and your card number (!). But, I must apply for substitution card in the branch where I open the account (that I would not pay a visit until the next three months).