Kristina Abernathy is now the only Monday/Tuesday fill-in, but she's not trained for HD yet I'd assume. (which reminds me of an audio clip I want to get up).
If both Rich and Sharon were to take off in an emergency, they might either resort to calling Adam and saying, "surprise, gang, but you're not off this Monday!", or they might call up someone from the PME crew like they used to do in the Dave & Hillary era.