Yes even when you have lost your admit card you can step into counselling. Only thing is you need to remember all the credentials which will be needed to log in to your account. And first of all, you don't need to worry as you can still download the admit card.

• Go to the official website https://www.jeeadv.ac.in/
• You will be able to see a link to candidate login portal. Click on it and a new window will pop up where you will need to enter all your credentials
• You will need to enter your registration number (starting with K which you must have got while registering for JEE Advance examination), your Date of birth, your registered mobile number and your email id
• In case if you have forgotten your registration number then also don't worry as you will find an option for the forgotten registration number and you can fetch it through your mobile number and email id
• Then after login to your portal, you will see an option to download admit card. On clicking it you can download it in a PDF format and later you can print it to use it for further process

Feel free to ask if you have any more queries. All the best!!