good story.
Couple comments.
If I get to a machine or bench and weights are on it and then I use them, I always re-rack them even if I didn't put them on in the first place. I feel that after I use it, that is now my responsibility. Someone after me wouldn't know that some other douche left the weights on. In your case it was 45lb plate, many women have a tough time schleping them around, leaving them on sucks.
As for the gas blast, someone did that at my gym yesterday and it basically cleared the area for a good 5 minutes. I wasn't able to figure out exactly who did it, but it was nasty as fuck.