"If she witnesses a coyote taking the dog...obviously coyotes don't Twitter!" McCarthy -- who has trained Kelly Osbourne and Christina Aguilera's pups -- tells Usmagazine.com. "So that would be essentially not very effective in this case."
McCarthy delivers sobering news about Daisy, who was given to Simpson by ex Nick Lachey.
"Unfortunately, if she saw the coyote take Daisy, the chances of it surviving are very slim. She's probably not alive anymore," she says, adding that the maltipoo may have been eaten.
McCarthy calls Daisy's disappearance "an important lesson...in coexisting with wildlife.
"We're so detached from nature as human beings. We have to understand, this is the circle of life and how it works," she says.
When will Simpson be ready for another pooch?
"Well it depends on each person. Obviously, people to go through the grieving process and losing an animal is a different kind of loss than even a human being because pets are unconditional love," she says. "Once she feels that she's ready to take that next step, hopefully from now on she'll keep them on a leash or take other necessary precautions," including carrying pepper spray and an air horn "to scare coyotes away."