I know someone who was recently hospitalized(Texas, US) but was not counted as a coronavirus patient because the test were negative(they didn’t test for anti bo

I know someone who was recently hospitalized(Texas, US) but was not counted as a coronavirus patient because the test were negative(they didn’t test for anti bodies). The illness resembles almost everything I have read about people with complications from the virus. Doctors & nurses when asked, they all say that for the anti bodies test, the patient would have to go some place else.