Recovery of registrants names and emails after cancellation of registration

We have postponed a zoom meeting that was going to take place on July 30. The meeting will now take place in September or October, date tbc.

I have just sent a 'cancellation' message to all our registrants, sending them a note to say the meeting is postponed.

I now find that the registrants box is empty and I cannot retrieve their names and email addresses. Can anyone please help?

Of course I now realise I should have backed this up before cancelling. However, there was no warning that the data might be deleted and I had no idea that cancelling would also delete data. 

Without their names and emails I shall be unable to inform the registrants of the new date when this is confirmed 😞