Sorry to hear that-
You can probably retrieve your number: if you provided your passport when you purchased the SIM you can bring that to a China Mobile office along with explaining what happened. If you didn’t, bring a list of 5 phone numbers that you called or texted before the phone was stolen. They will take the list and check it to your phone records, and then give you a new SIM with the same number that you had.
Out of curiosity, how was the phone stolen?