I can't give any such example. However, EVERY economic collapse has been followed by rebuilding. Maybe the nation has a new name or new boundaries, but something is always rebuilt. And once it is, gold has value again.
I hear Bitcoin is popular in Venezuela, where the people hunt pigeons for food after the communists took over. It's also popular in China, where - again - people are scared of their government.
I don't know that the US federal government is as scary, but it's not unheard of.
Oppressive governments are essentially the only good reason to use bitcoin, since the usual financial system is far more efficient at storing and transmitting money. He's either evading taxes or speculating.
My bank charges $40 + 2% forex spread for a wire transfer to Thailand. With Bitcoin I actually come out at a small profit. Bitcoin is way better at consumer level international transfers than banks.
Even generally non-oppressive governments make errors, and it happens more often that you'd think (and suing might be prohibitively expensive, untimely, or not an option at all).
The usual financial system is far more efficient at converting your wealth for the use of the oligarchs. USD for example has lost almost 100% of its value since the institution of the Federal Reserve system. The wealth did not go away. It was merely transferred from the populace to the rentiers.