Oh! Stress is the cause to not remember at all what you did with something right in your hands. Your mind was going too fast thinking of other things.
I have never sit a trash bag anywhere in the house just to sit there. Plastic bags from stores get thrown away as soon as they come in the house. I don't like or keep plastic shopping bags (or wire hangers, lol) If one is sitting out DH or the kids will know it's odd and will ask what is that?