There are always millions of tons of dust in the air, just as there are millions of cubes of air in the earth…And sometimes there is a ballpoint pen in your washing machine, which explodes and does this to your bathrobe:
But why did it have to be the load of whites? Some quick googling turned up an effective solution: rubbing alcohol. When it comes to stain removal always remember the chemists' adage, like dissolves like. Soap and water will work on water based stains. This is also why your nail polish dissolves in nail polish remover (acetone), but not in water.
The final result was great. You could barely tell the robes had been stained at all. There were points along the way where we thought we were going to have to buy replacements. Fortunately, instead of shelling out hard-earned cash, we were able to salvage them with chemistry and a little elbow grease!