Hello There!

As you have not mentioned the exam name or organization name for which your daughter has lost the registration number. I would be able to help you in a better way if you could mention that.

Generally, when you create an account or apply somewhere to any organization, the registration number is mailed to the respective/registered mail id. Or when you do any payment for same application, again you recieve a mail or text message regarding same which consists of the registration number. If you are still not able to get it, I would suggest you to contact the authorities either via mail or phone.

Thankyou!