Nope, you just do no report it and they can not verify you have not lost, given to charity or invested it in a way that it cannot be taxed. Regardless once the money is outside of reporting to the IRS they can not tax it in the past and cannot assess it for future taxes.
Only if you somehow move it to a reportable entity going forward can they get to it. Do you really think there are no tax havens these days?
Oh I do know they can hide it, but the IRS can track it if they want to as well.
It just depends on if they want to target you or not. I mean the gov’t illegally wiretapped a President...do you really think they wouldn’t do the same to a normal citizen?