Originally Posted by
UAPremExecflyer
I doubt UA will short-check your bag as that will raise questions about a re-fare of your ticket (and could be very expensive).
With a 9-hour layover, I would think requesting the agent in STL to short-check shouldn't be a problem. As the OP I'd tell them that, due to the long layover, I have booked a transit hotel and will need to access the contents of the bag.