"Kelly told ABC she wasn't coming in last night," says the source. "They don't know yet when she'll be back."
Another TV source says Ripa is currently "refusing to come back" and that while she could decide to return any time, her plan is not to for the rest of this week.
A different insider told PEOPLE Ripa was "completely blindsided" by the Tuesday announcement that her co-host Michael Strahan would be leaving the talk show to join Good Morning America as a full time co-anchor in September.
Of Strahan, 44, the TV source says: "He's a class act. He's trying to do what he thinks is right, that's important to him."
A rep for Live! told PEOPLE Ripa "had the day off," and Ana Gasteyer filled in for the star Wednesday morning.
Strahan, 44, meanwhile, took a moment to address his co-host of four years at the end of Wednesday's segment.
"I really want to thank, of course, Kelly Ripa," he said. "Kelly welcomed me here, and I've learned so much from her. She's just been an amazing influence on me and this has truly changed my life to be here with her."
"And I know that the show will continue to be strong and great because of Kelly ... and the staff here because everybody here is so talented," he added. "This show has not been around for over 30 years by mistake."
"Kelly, I thank you. I love you and everyone else here at Live!, and I'm not going to cry on TV momma, I promise you," he concluded.
Live! With Kelly and Michael airs weekdays (check local listings).