I think using event id + author is a better scheme than event id + relay.
Discussion
May I ask why is it a better scheme?
In which way is it better?
* event_id + relay gives you the required info to get the full event.
* event_id + author requires you an extra step: knowing author-relay relationship.
In some cases, yes, but one doesn't negate the other. I'm just saying event id + relay is not stupid, it actually kinda works.