Yes I know how blockchain works
You don't:
Please provide wallet address
It's posted
here.
That doesn't show the original BTC address where the 13BTC originated from does it, it just shows the mixed BTC and where it was sent to.
Why not?
If this moron stole/hacked/scammed 13BTC, and someone steals from him, tough titty.
"If". And it's a fallacious argument even without the "if". Outside of good-guy-takes-down-a-bunch-of-bad-guys-and-saves-the-girl movies, stealing from a thief is still stealing. But don't let that distract from your intertubes tough guy act. Let us know how that letter works out for you.