After she was nowhere to be found on the ground beneath his balcony, Isfeld immediately went searching for her, going floor by floor in his building.
She was nowhere to be seen, so Isfeld posted his concerns about her the next day on Facebook.
The response, he says, was amazing — with so many people sending messages and trying to help find Cleo.
It wasn't until 11 p.m. on Monday night that Isfeld received word Cleo had been seen on the terrace of an adjacent building.
"I didn't know if she was OK ... if she was injured. I was in tears," he told CBC News.
"She was shaken up, but other than that she was totally OK. No broken bones, no scrapes, just a small cut on her mouth."
The Savannah cat is a breed known for intelligence — and, in Cleo's case at least, having a sense of adventure.
Asked how many of her nine lives Cleo has used up, Isfeld said she was running out.
"She's only got a couple left. She is a pretty cool cat."