I have military grade weaponized sweat. In large quantities. All my stainless carry guns get a little rust now and then. Under the grips of revolvers, in the slide serrations on autos.
I actually found rust rust inside the barrel of a K9 once. (Carried appendix).
But, I have to carry them against my sweaty body to get rust. Perhaps your gun was not passivated properly.
Remoil may may not be the best. It's really a dry lube when the carrier evaporates.
CorrosionX is good stuff, but stinks. Boeshield is awesome, but a little waxy.