The engine in the LS has 3 belts that would slip (causing a squealing sound). One drives the alternator. One drives the power steering. The other drives the air conditioner. You won't overheat your motor because the water pump is not belt driven. Well, it is, but it's driven by the timing belt, and if that had broken you'd know it because your engine would quit and you'd have heard the lovely sound of your valves being destroyed by the pistons
So relax on the belt issue - that's not what's wrong unless your steering is stiff, your air conditioner doesn't work, or your battery light is on.
I think you somehow got something between the rotor dust shield and the rotor on your brake. And I think it finally fell out, whacking something on the way out (that's the clunk you heard).
Bottom line? Probably nothing wrong at this point.
But while we're on the subject of belts, how many miles are on the car? If it's more than 90k, and the timing belt has never been changed, go get it changed yesterday. That thing breaks and you'll be rebuilding your engine's valvetrain.
No way to check for signs of wear because the timing belt is located where you can't see it just by opening the hood. It's a BIG job to get down to it, and if you don't know anything about cars, you don't want to even try.
BTW my first thought was brake pads too, but they shouldn't have stopped making the noise, so that's out.
It is most definitely NOT a wheel bearing. A bad wheel bearing makes an annoying low pitched grinding noise that gets louder if you put more weight on that wheel (i.e. you turn the car), and like the brake pads, a bad wheel bearing will not suddenly stop making the noise.