That’s always been my theory, they knew in advance Duncan was exposed to Ebola(He probably told them before he left from Liberia) and they left the apt, they were never in that apartment to begin with
If the family was not in the apartment, then where were they? The GF's daughter had an apartment in the same complex so they could have gone there I suppose. Then they would go back to the apartment on Sunday just long enough to call the ambulance and see Duncan off to the hospital. Then left again and come back just for the Dallas officials to come and take them away to their new home.
All possible, but none of it is likely.