I am confused about your last sentence "which was determined not to be the tenant's fault" so I do not understand why money was withheld?
But, I want you to stop for a minute and think about it, how much is the amount? does it worth your time and aggravation? It is very likely not worth hiring an attorney for it, since it will cost you more in attorney's fees.
Also, you mentioned that it was determined that it was not the tenant's fault! who made that detonation? is it the court? or it is the management company? use that evidence to your advantage.
It's most likely a corporation, not an individual. That's OK. You sue the corporation. They'll have a registered agent in Virginia. The State Corporation Commission in Richmond has an online service in which you can look up any registered corporation.
Though I understand your feelings toward the management company, if the court said you have to file against the property owner, then you have to file against the property owner. Tip: If you do that, the property owner won't be happy with the management company. So your issue with the management company will become very apparent to the owner.
Fairfax County also has a tenant's rights office. I don't know its exact name, but just call the county or look it up online. (The Better Business Bureau is worthless in these matters. Understand that the BBB was set up by businesses to protect business interests, not yours.)
Hope that helps.