With his credentials available, why wont you report this to your, or even Polish court? As far as i can tell, it will be possible to do something about your btc (or their value in cash) if youre interested and got enough time/patience.
Polish law system is surprisingly effective, when facing an opportunity to get some tax back, calculate a fee, etc.
You can go as far as 6 months to 8 years for a proven fraud, not to mention all the weed stuff.