No! This type of show is live and although it should not happen, it sometimes does. In the movies, they have weeks/months to look over the film and retake the bad scenes. I give you full points for noticing but none for the slipup itself.
If the boom mic is all that you wre able to see, then thats pretty good. Things like that happen more often than you might think in live TV. Just a side note...The Late Show is actually taped around 530 in the afternoon, and then is edited down..it is basically taped exactly how it is seen on tv. It is also not uncommon to see the studio cameras in the background of some shots. It's really not a big deal, and thus cant really be called a slipup.
So? It's a talkshow. If it was a show with acting, that would be bad, but this isn't. It doesn't matter if the mic is there. You can see other cameras sometimes too, but these things aren't slip-ups.
The boom mic cant count as a slip up. This happens quite often. Once on The Tonight Show back when Johnny Carson was still on, Burt Reynolds actually reached up and grabbed the mic when it got too low once.