How do I recover disappeared shared Calendar events on iPhone?

I had a shared calendar with my son. I have realised the events for the last year on my own iphone calendar disapeared. And now I checked my son's iPad and the events on the shared calendar are also not there. He still has all events from over an year ago in his iPad, same as I can see in my iPhone. If events disappear on my iphone, owner of shared calendar, will also disappear on non owner device, in this case my son's iPad? I tried to recover for a previous version of his calendar in iCloud on web, but still nothing else shows up. I can't precise when things disappeared in my iPhone, most likely in the past month at most, but only today I realised. Any way to recover a shared calendar events if it disappears from calendar's owner device?

[Re-Titled by Moderator]

Original Title: shared calendar events disappeared