wow, I guess you guys are a bunch of newbies. Its probably the most famous(try googling it & see how many articles come up) match of the last 5 years. It wasn't that long ago(2004) & was kinda at a big event(US Open QF)
That match is the sole reason instant replay exists today.
And yes Serena lost that match. The USTA president apologized to Serena the next day, the umpire was dismissed from the US Open(not sure she's ever worked again) So yes umpires are held accountable for screwing up.
What's most interesting to me(& no one ever seems to mention it) was that the umpire never audibly overruled(linesman called it good) so not only was it a bad call, but an illegal one, you have to let the players know you are overruling, not just announce the score. If Serena called the referee out & mentioned that, I have a feeling they would have at least played 2. But she was too upset to even think about that part(Mac & Connors never would have allowed that to happen)
Maybe the umpire really just lost track of the score, since she never said 'correction' & was just trying to save face. The whole thing was strange.