Help please, Questions for Emergency room visit, many thanks

Last Dec 13, I took my daughter to emergency for extreme stomach pain. They did test her throat and urine there and they told me everything is negative. After stay there for several hours, they realeased her. Now I'm reading the medical record for that day, I found out actually the test result showed that she was positive for Strep throat, which was verified on Dec 15, 2012. But nobody let us know the test result until now I found out by myself. Legally, does the emergency room have the responsibility to let us know the result ? My son and my husband was diagnosed with strep throat days after that.
Thank you for your patience in reading. I just couldn't type Chinese in this stupid computer and many thanks for your inputs.