since you are doing the test at home, and are suspect of the virus being on the swab itself, why don’t you test the swab as is?.....if there is virus, it will show.....then tell the company that your swab slipped and fell on the floor, could you get another testing kit?...
Good suggestion
Yes, you should do one without bodily sample, clean, as a control.
Then pee. Mangoes. Penguin poo. Tissue snot. Etc.