Hi, I have a doubt regarding MS application for Computer Science. For GRE test score registration

Hi,
I have a doubt regarding MS application for Computer Science.
For GRE test score registration is available only for most recent test given. But I want to apply with my old score for which I don't have the registration number. I called the ETS care and they said that there is no provision to get the previous GRE attempts registration number. I can only access the appointment number for those attempts.
Please let me know what should be done in such case, if my previous GRE test registration number is not available.