Another example of this is “find out” and “know”.
First, we FIND OUT some information, and then we KNOW it.
So when we talk about the first moment that we learn some information, we must use “find out”, but we can’t use “know” until afterwards.

For example:

I found out about the terrorist attack when I watched the news report on TV. I was so shocked!

I knew about the terrorist attack before I watched the news because my friend had told me about it before.