Could be a simple case of Viral Gastritis.. all reports in that case might be normal.. In case of viral infections of stomach.. all the reports will be normal. in some cases body immune systems fights with germs well and flush out the germs via vomiting ( in some case even loose motions might be there). You should feel, happy that nothing serious had come out in reports. But if this condition, reoccur or there are other associated new symptoms, then your doctor will have to re evaluate it. Sometimes disease evolve our time and final diagnosis can not be made at first episode of illness. Have faith in your doctor.

May be stomach infection only. Wait and watch for the time being. If he responds with Medicine it's good. Sometimes all test comes normal but still patient is symptomatic so we have to treat it.