Could amniotic fluid test be wrong?

So I thought my water broke last night. It was like nothing I'd experienced before. It felt like I was peeing myself, but I haven't had bladder control issues at all and this definitely wasn't urine. It was enough to soak through my underwear and shorts and run down my leg. It didn't continue to leak, but a couple hours later I started getting contractions. I eventually went to labor and delivery and they tested for amniotic fluid which came back negative. Has anyone ever had the test be wrong? The test was taken about 6 hours from the time I had the "discharge" if that makes a difference. Also I'm 39 weeks 2 days, 1 cm dilated and they said baby's head was right there. I have been having contractions for more than 12 hours, but not consistently enough for them to keep me.