The stainless steel didn't rust. The cast iron pan was accidentally left on the corner of the sink for a weekend with a little water under it. The rust wiped off very easily, because it was transfered from the iron into it, which is all that's happening as long as it's not left there for a significant amount of time.
The truck was driven in rain, with no snow or salt involved, and began rusting after 2 days. That's a low grade of stainless steel to rust that fast.