Re: Russia, Trump, etc.

But if there was American help, Comey told lawmakers in early June, “Director Mueller will find that evidence.”

So, the word if has some context here.....
One could say Comey knows of no evidence then when he made this statement.
To further that observation up, he remarks Mueller will find it.....as in, they don't have it presently, and "if" , it exist, would still be in context.

Here, read the story yourself.

But if there was American help, Comey told lawmakers in early June, “Director Mueller will find that evidence.”