I have tried to fill a few of the large bag orders (20 slot) but each time I contact the person who placed the order to request they send me the Rune, they have no idea what I mean by that. It does clearly show in the upper left hand side of the page when you place your order that the Rune "Must Be Provided By Player".
Is there some way to highlight this more for someone at order time? A popup confirmation pointing it out to the buyer before final order placement? A system mail to the buyer that they will be contacted for their player provided goods and be ready for it?
Those are just 2 ideas, I am sure there are other good ways as well.