Help! I flew ORD-LAX 7:30pm arr ~9:30pm. Surrended by "systemwide" at check-in at ORD.

Following morning when checking in for LAX-HKG agent made me surrender another systemwide...I raised a huff, since ORD-LAX was not considered a stop-over [less than 24 hours]; the supervisor came over and made a number of calls and said that the systemwide one-ways are only good for one day...

Obviously returning from the Asia you never lose that day...but I feel that I was ripped off for one systemwide upgrade.

Did I misconstrue the language? I'd like to know the experiences of any others...since I had to return to the West in economy...the one I had to surrender at LAX was my last.

Thanks!