comedy option: visit as a tourist and show up in their office.

I did this to someone who ripped off my master's thesis, word for word, as a side trek on holiday and it was like steam came out their ears when they realized if they call the campus authorities to escort me out they'd generate an incident report of why I was there.

Edit: This was not in China btw -- ironically despite the stereotypes all the folks I've collaborated with from there have been pretty ethical and hardworking, it's a shame some ruin things for everyone.