Oh my. Sounds like it all went wrong for you. Willows will root in water and also will help other plants to root if you water them with the water that the willows were in. Never strip off all the leaves as the plant needs some to make food. Just remove the ones that will be below the soil line when rooting.
Totally enclosing your cuttings in plastic without any air holes for circulation probably caused a fungal problem and/or rot. Putting them in sun with the plastic will cook them. Take a look at these sites. Oh, you don't need rooting hormone for willow. Many times you don't need it at all.
Hope this helps,
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.