Thanks for all the replies guys! To clear a few things up things:

- The front plate was still on the bike, that's why i'm not sure if i lost it or it was stolen. No bolt stays tight on a chinese bike very long...

- The fake plate is and exact copy with the same numbers as before, i got it from "some dude". It cost 350 and came with front and rear plates and even those special tamper-proof bolt covers with the 沪 symbol on them.

Getting the legal replacements would require getting a report of the theft from the police. I haven't done that because i don't want to draw attention to the bike or owner, especially as it's registered under someone's company. My friend says it's fully legal, but i don't know how legal is legal. I'm sure some numbers got changed on the frame at some point... As LJH said, going to the police out it might end up in someone saying this bike shouldn't be registered in the first place.

Two years ago the rear plate fell off my XTR250 and i went through the legal replacement process. It took two and a half months and required me to make two trips to nanjing (where it was registered) which is not even a fun ride.