Moss recalled her reaction to Piven's departure from the 2008 play, which he blamed on mercury poisoning from eating too much sushi, during a recent interview on Bravo's "Watch What Happens: Live."
"That's a very good one. I could go on and on, being highly unprofessional," Moss replied when asked about why Piven exited mid-way through the production. "We were all surprised. It came out of nowhere. He just didn't come back one day. ... I saw him like a month later at the Golden Globes, when he was supposed to be really sick."
Norbert Leo Butz and William H. Macy ultimately replaced Piven in the show.
Moss is best known for her work on TV's "The West Wing," "Mad Men" and "Top of the Lake."
Piven is a former star of "Entourage," who can now be seen in "Mr. Selfridge."