Dear Raja, As far as my information goes, the ESIC office does not give any Registration Copy to the Employer for its establishment's coverage under the ESI Act. Rather, they provide only a Coverage Copy where your establishment code is mentioned.
Section 10B of the EMPLOYEES' STATE INSURANCE (GENERAL) REGULATIONS, 1950:
(d) Upon receipt of the completed employer's registration form, the appropriate Regional Office shall, if satisfied that the factory or the establishment is one to which the Act applies, allot to it an employer's code number (unless the factory or the establishment has already been allotted an Employer's Code Number) and shall inform the employer of that number.
If you want your coverage copy, then you may contact your appropriate Regional Office, and they will provide another copy. They do not need any form for that.
Additionally, you may lodge a General Diary with the local police station for the loss of your establishment's Coverage Copy before going to the Regional Office. Submit the GD Copy with a photocopy of your coverage copy. I believe they will provide another Coverage Copy with the same number.
I hope I am correct.
Regards,
Jawed Alam