To recap your position, it seems like you have one ticket from YVR-PVG-ICN (<--guessing) and another ticket from PVG to your_hometown. But the trans-pacific leg is the original ticket. Is that right?

Since you will technically be a "no show" on the original ticket's PVG-ICN leg, you may have difficulty getting this done, even if the ticket agent in YVR allows it. US airlines have been known to cancel both legs even when they identify you as a possible no show.

If your layover is still 9hours, why not just check the bag only to PVG, telling the agent that you just want the bag when you get to the other end, and you can recheck it to your new destination at PVG?

Sure, you may still have to get the bag at PVG customs no matter how you check, but with the bag checked only to PVG, they won't be expecting it on the original second leg.