Based on some other reports, it sounds like it was a fellow audience member who was noticeably taking the cell-phone user to task. It was noticeable enough to get Foster's attention, and she stopped the show to ask if something was wrong. When the audience member said that the woman was refusing to turn her phone off, that's when Foster said, "Okay, we'll wait." Definitely not a LuPone-level freakout.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body