Not all bed bugs live full time in the bed, they can live in recesses around the room and the loft, just coming out to feed on the sleeping victims. They can travel across the ceiling and drop (without parachute) directly onto the bed or the victims themselves. Many years ago, my wife and myself bought a cheap little terraced house in Salford near Manchester. We'd just finished decorating right through, when there was a sudden heatwave, which brought out the bugs. We only had lino on the bedroom floor and at night you could hear the bugs landing on it. Needless to say my wife, wouldnt enter the bedroom and slept on the settee downstairs. As she was pregnant at the time and the bug specialists unable to come for two weeks, we handed the keys back and moved out.
Fumigation seems to the long term answer.
Dave.