where's george?

Today I discovered that one of my $1 bills had a red stamp on it with a website: wheresgeorge.com. I happily spent my bill (serial # K55108582A) at the enchillada cart by my lab and then returned to claim my place in currency transaction history. Alas, you also need the series to properly enter any currency. I guess I could go back to the enchillada lady and explain that I need to look at my slightly wrinkled George Washington, but that seems like it would cause some confusion.