I reactivated my PPL after a 10 year break just under a year ago so have a little while before I need to get things done, but I would like to be prepared!
.. .. but how exactly did you reactivate it?
Presumably with an instructor in which case I think you need to have a chat with him and ask where your certificate is.
The good news is that as matters stand your license is non expiring (although EASA will probably determine otherwise in due course) but your license is only valid when accompanied by a revalidation certificate.
(All that said whether the certificate MUST be completed on the CAA provided "form" or can be written up in some other way, I dont know.)