Unless you loose your Altimeter/ASI or you Compass/DI i don't see how it is possible (unless some control surface failure occurs). I don't have my IMC yet (booked for August), yet i fly at least 3 times a week from the Isle of Man to somewhere (Newtonards, Dublin, Liverpool, Bristol...) quiet often there is no horizon and plenty of haze. For me it is common sense to look atthe instruments (usualy ASi and DI) i find if those two are saying what you expect then all is well (obviously i check the other insturments). I think it is logical to say if your airspeed is not right then the plane is doing something that is most likely going to ruin your day if you dont sort it out.