A crime is also a crime even if no one gets caught. Just like one can break the law and never get caught. Might want to be careful with these statements though, your leftoid buddies have made claims that one can not commit a crime unless caught AND convicted.
And stated that if the Government never charges you, you never broke the law or committed a crime.
Can you guess who they were defending with these claims?
Was it Bill Clinton? Clinton was guilty of contempt of court for lying about his relationship with Monica Lewinsky, and he was properly adjudicated in contempt. But you're probably thinking he committed perjury, and that isn't so.
Perjury is lying under oath about "any material matter which he does not believe to be true". A material matter must be both relevant and significant to the matter being tried.
In discovery proceedings, the standard is much less. Clinton was obligated to reveal the relationship in discovery because it could lead to other evidence that was actually relevant. That omission was properly punished as contempt. But Clinton's voluntary affair in the mid 90's did not tend to prove anything that was at issue in the Paula Jones case. It wasn't relevant, and it certainly wasn't material, so the perjury statute simply did not apply.