Dear Aspirant,

In most of the cases of lost credentials, you have a way to get them back. The most popular way to get it back is E-mail. The way to get it back could be either online or with a helpline number. ICAI has sent you a mail regarding your registration number, check your mail list. However, if you do not have it then contact ICAI, mail them regarding it, they will revert to it.

Hope this helps.