Worried about possible negative urine screen from pain management

[Worried1027]

I see a pain management doctor for severe knee issues and am prescribed 1 Norco 10mg twice a day.  I went in today (4/10) for my normal apt and they did a urine screen. They asked when I took my last pill which was, as directed, on 4/8 - it had been over 48 hrs since my last pill by the time they collected the urine. When I got home, I realized I forgot to mention that I had a severe stomach bug (throwing up every 30-45 mins), so I can't be sure I kept any meds down since before that started on 4/7. I take my meds as prescribed, and am very worried about a negative urine screen. I've been seeing this same doctor for over 7 years, without issue. I stopped taking the norco to have two children (most recent born in January) and have just recently been going back to see her again. What happens if the test comes back negative?  Will I have a chance for a re-test?  Are there legal consequences?  I don't want anything to happen to my children, I'm so worried.