From Anne Schroeder (a day late):

And yes, that was Christina Aguilera at Mie N Yu in Georgetown Saturday night after her Baltimore concert. She arrived around 1 a.m. and left two hours later, when she was then spotted climbing the fire escape entrance/exit into MCCXXIII-Spank. She stayed for only a few moments before heading out, presumably to bed — although she is a pop star, so you never know.

 And from us, yesterday.