You are misinformed.
Trump has denied the Flynn conversation.
"Asked during a news conference in the White House whether he “at any time urge[d] former FBI director James Comey in any way, shape or form to close or to back down the investigation into Michael Flynn,” Trump responded flatly, “no.”
Trumps tweet about tapes was in regards to conversations in general and didn't specifically mention the Flynn conversation, and implies that the tapes would show Comey to be wrong about what was said.
"“James Comey better hope that there are no ‘tapes’ of our conversations before he starts leaking to the press!” the president tweeted yesterday."
The possibility of this crime is currently being investigated by the United States Congress.
This is a little bit bigger than just some mistake. Even if it is deemed to not be criminal, it was certainly serious and concerning to a lot of very high level people.
I am thankful that most people disagree with you.