See if you paid the fees then you can check the status of the payment on the official website of the ICET by logging in with your valid id. If its shows paid then you have nothing to worry about the reference ID.

Now sometimes the gateway through which the payments are done sent you a email of reference ID to your registered email address. So you can check your email if there are any of such emails. Also you can update your bank passbook in order to see if the money is deducted succesfully and also there some sort of ID is provided which may or may not coincide with the online payment ID but you can use it as a document.

To know more about ICET visit the link below:

https://www.careers360.com/exams/tsicet

I hope this answer helps. All the very best for your future endeavors!