Let's say someone well-intentioned but distracted, an overall good guy who doesn't deserve his wife's wrath for making an easy mistake anyone could make, let's call him C, left 4 sets of sheets and damp towels used during the last guy's weekend at the lake in a trash bag sealed in a storage tub in the garage for, say, oh, quite a while.

And let's say the normal cleaners got the smell out, but not the stains from the mildew on these sheets and towels.

What should this good guy use to remove the stains, so he doesn't have to go buy 4 new sets of nice sheets and towels? Is there a product that has worked well in these cases before? I mean this has got to be common; anyone could make this mistake. Right?

Provided the stains aren't from the mold actually digesting components in the fabric Oxyclean has saved me quite a few times

Yeah- if Oxyclean doesn't do it, head to Bed, Bath & beyond.

Let STECZ use everything and the stains will transfer to him.

I'd say a trip to Beds, Bath, and Beyond is in you future.