How do you deal with exit entry visa stamps?

this is to Mr Johan, who gave me this reply,
"I applied for a z visa from China, I sent my documents and my second passport to a visa service provider in Sweden. They sent my passport with z visa back to China, I left China and re-entered without having to go all the way back to Sweden."

I want to know, if i post my passport back to a friend in Australia who can get my passport stamped with a new visa, my z visa while i stay in China, how do you get around the lack of exit and entry stamps on the passport? Can my friend just post it back to me and i go to Hong kong and back to get the stamps and then everything is above board????? Please help, i really can not afford the time or expense to fly back to australia just for a stamp! Thank you in earnest