I don't want to go into too much detail, and I'll speak hypothetically. First, always carry an ID card with you when you travel, from your home country, as well as your birth certificate, incase "something" God forbid happens to your passport, like it get's stolen oo something. Also, keep a phot copy of your passport with you, again, just in case it is stolen. This also gives you something to show the police when and if it is ever stolen, and yes if it's taken you must report it to the police.

If your passport is stolen, make a report, and head right to the US consulate, and apply for a new one, with your ID and birth certificate as proof, as well as the photo copy of your old one as a trump. Than you just wait. Once you get your new passport, go to a visa agent, shop around because not all have any connections, I got lucky, and if anyone wants to know how I used, just email me.

Anyhow, the next day you'll have a new visa and you can return to China. Now this is all only if God forbid your passport gets stolen, which would be a shame.