I have a purchase ID that gets passed to msevtmgt_FinalizeExternalRegistrationRequest along with the readable event ID, but once I have called it I can't find a way of locating the Event Registration that it has created. I had assumed/hoped that the purchase ID and registration ID would be connected in some way, but with extensive searching I can't find the purchase ID Guid anywhere in Dynamics.
Is there any way of connecting the purchase and the registration? I could do a search looking for records created shortly after the registration, but that's not 100% reliable.