I can only imagine how frustrated you must be and how unhappy you are with the homeowner. Both Konnie and Cindy gave great answers. I, too, will suggest that you contact a real estate attorney and that you check out the Prince William County website. Look for the links to housing or foreclosure. I know you said it is a short sale, but you will see the section on tenants rights. You might also want to look at the Fairfax County goverment website (www.fairfaxcounty.gov) following the housing links for more information.
Your lease will tell you if the homeowner can put a lockbox on the door and what the procedures are for showing the house and notifying you prior to any showings. It is in the homeowners' best interests to let you know when an open house will be held (usually on a Saturday or Sunday, during the afternoon, so that you can put away your personal belongings and straighten up.
I hope things will work out for you soon.