Pull over and see the alternator belt has snapped, think ok well I'm only two minutes away from home should have plenty of charge to make it, carry on down the road and hear CLANG CLANG CLANG and look out my drivers side window to see a pulley wheel rolling into the bushes!!! Stop and look for quite a while but have no luck finding it!

Just trying to figure out which wheel it is exactly, the one that is missing is just below and to the right of the alternator wheel, I need to know so I know which part I am looking for.
And I apologise in advance if people find this stupid to ask lol.