Did It Really Happen?

A short note on existence and false memories.

In the 20th century, doctors believed that babies were unable to feel pain. It wasn't until the late 1980s that they had begun administering anaesthesia while performing surgeries on them. Obvious indications of pain were displayed when the painful surgery would be performed in babies, such as crying, thrashing, violent behaviours, and other such expressions. This was ignored. 

Individuals are unlikely to remember specific events before the age of 2 and a half years. Any memory before that age is likely to be false. This phenomenon of being unable to remember childhood events is often referred to as childhood amnesia, and the average age that humans are able to create and store memories is four years.

Did the pain really exist, then? Yes, babies may have felt pain during the surgery, but if they are unable to recall it—did they really feel pain? Disclaimer: Obviously, performing surgery without anaesthetic on babies is inhumane; I'm not a sadist. 

Without memories, there would be near nothing to give proof of the existence of an event. Video cameras can give proof to an event, but, with the rising of the digital age, even videos can be manipulated.

I've often heard stories about my younger (and, evidently, more foolish and far more naïve) self, and, most of the time, I find myself in an awkward situation in which I am unable to remember any of the events that Mom would be laughing about. To me, they didn't exist—and they never will.
If all affected individuals of that event (all "witnesses") were to forget about it, would it still exist?

However, it may also be argued that most events trigger other events, causing a chain reaction known as the butterfly effect. As such, there is the possibility that an event could leave a lasting impact on the world without anyone having remembered it, thus consolidating its existence.

This is my question: If the event was neither able to nestle its way into someone's memories, nor able to trigger a chain reaction, would it still exist?