I worked in a bearing factory and had as a desk paper weight a complex shaped helicopter bearing race. It was blued like a gun and dipped in a preservative oil..
One mornig I came in and saw a perfect set of finger prints in rust !! I asked those who had been in my office the day before and found the culprite !!
He admitted he had a problem with that [in a bearing factory ! ] They make special soaps and lotions for people like that .
Oxidation can take place in a fraction of a second .That can be easliy demonstrated in a laboratory.
The bearing example is fairly rare but oils in you fingers can contain a number of chemicals including salt , that can cause rust.I even came across a federal inspection specification that stated "this operation will not be done by women " This because at certain times of the month a woman's chemistry can change greatly !!
It's always a good practice to wipe down a gun after use with oil.
I use a rag with RIG grease.