I think your odds are much less than 50-50 because I don't think they will accept your bona fides. The round-trip ticket will suggest you planned to do this. And you don't seem to suggest you're seriously ill.

If they do let you through, it's in the Chinese bureaucratic nature for there to be a cost, perhaps a ban on future use of TWOV.

If you're ethnic Chinese, expect even less sympathy from officials.