I think you should contact your local Congressman, and send him a bill for the $6. After all, you were not expected to pay, and you did....so, you should have a refund coming!
If your Congressman doesn't return you calls, just assume that he's busy right now.....trying to avoid the Press.
You may just want to put a comment on your 2013 Income Tax Return, as this appears to have become a "donation"....that is of course, if the IRS is even working next April?:S
At least you had a great time....that is more than a lot of folks can say, who apparently had more astute Rangers, who actually cleared people out of the CG before they closed the place down.
Happy Camping:)