I don't want to cause any alarm (or more than needed) but usually, it's the bottom hose that gets sucked flat. If the problem is not the radiator cap, it could be the pump. The bottom hose is usually on the inlet (low pressure) side of the water pump and that's why there's a spring in the hose so it keeps its shape. The top hose is under pressure and retains its shape. That's the way it usually is (from my experience).

Anyway, it appears as though your top hose is now on the low pressure side, which might suggest that you have a reverse rotation water pump installed. My understanding is that there are two types of water pumps for the 3.0 motor, standard and reverse rotation (although I have to admit I could be getting it confused with another motor). I know of other people who have gotten the wrong rotation pump from the parts store. If you have a reverse rotation pump installed, then the top hose would be colder than the bottom hose. If the top hose is really supposed to be the one on the low pressure side, it should have a spring in it to keep it from collapsing. If the hose is old, the spring could have corroded away.