The latest S2000 machine I've seen is 2007. I think that's when they stopped making them, or 2008.
I don't know any way to trace a slot to where it came from. I only know where two of mine came from because I bought direct from a dealer that purchased them from the casino.
$126k over your machines lifetime doesn't sound like much. Your machine was probably cleared after it came out of the casino.
A lot of casinos still keep small banks of S2000 slots for folks that prefer the older style machines. As far as replacing machines with newer technology, I doubt the gaming commissions have any voice in this. It's a matter of casinos stocking what people like to play and keeping up with the changing styles and games.