Yes, Milo is found safe and sound in All Her Fault.
Based on the book, All Her Fault by Andrea Mara, the Peacock series features Sarah Snook, Dakota Fanning, Jake Lacy, and Michael Peña in the main leads. The mini-series soon grabbed attention after its release for its intriguing storyline of a mother who is in search of her son, Milo, after he is kidnapped. The series received 7.5 stars on IMDb.
As for viewers wondering, "Is Milo found in All Her Fault?," there's good news, as Marissa and Peter's son Milo is found by the end of the series.
Why is Milo kidnapped in All Her Fault?

Marissa and Peter's son, Milo, is kidnapped by Carrie Finch, another character in the series, who thinks Milo is her son and wants him back. Carrie's real name is Josephine. Marissa, being a busy mother, decides to fix a playdate for Milo. Later, she visits a lady's home to pick up Milo, only for her to hear that she doesn't know any Milo.
She also reaches out to Jenny, the mother of the kid with whom Marissa fixed the playdate. However, Jenny didn't know about it either. This leaves her in shock and anxiety, thinking about what happened to her young son.
While Milo wasn't with Jenny, he was taken away by Carrie, who worked as Jenny's kid's nanny. Marissa soon understands that someone pretended to be Jenny and took her son. The investigation soon starts unfolding the details of the case and the truth that was kept hidden. It's revealed that years ago, Marissa, her husband Peter, and their child were involved in a car crash alongside Carrie and her newborn son.
In the accident, Peter and Marissa's child dies, and Carrie's child survives. Peter, who was conscious after the crash, chooses to swap the children, taking the living baby for himself and leaving the deceased baby with Carrie, making her believe her child had died.
And though Carrie believes it, she later meets Milo, and through the shared traits, she comes to realize that her son was never dead. Turns out, Milo is Carrie's, aka Josephine's, son. She starts building a bond with him and comes up with the plan of kidnapping.
Is Milo found in All Her Fault?

Yes, Milo is found in All Her Fault. Carrie takes help from Kyle and Rob for the kidnapping of Milo, who she believes is her own son who got swapped in the car accident. While Carrie kidnapped Milo as she was emotional towards him and didn't want to stay away from him, Rob, Carrie's father, decided to reach out to Peter for money in exchange for Milo.
Peter, who had known the truth about the swap all along, decided to go to the location with the cash and eventually killed Rob in the process. However, he didn’t want to be caught, so he put Milo in his car trunk and left the vehicle near the police station. He also kills Carrie after she comes to know he killed Rob. Police later discovered Milo in a safe state.
Marissa is relieved after finding Milo. However, through further confession, it's revealed that Peter caused an accident that left his younger brother, Brian, paralyzed. However, he never accepted it and blamed his sister for Brian's disability. Additionally, Peter also never told Brian about the surgery that could have helped him with the disability.
Speaking of his character, Jake Lacy, who played the character of Peter, said:
"Peter just wants to see himself as the 'white knight.' There is justification for the actions he's taken, but his inability to own up to them ultimately is his downfall."
What happens to Milo's father, Peter?

Peter Irvine also died by the end of the series after Marissa came to know about the truth of Milo and the lies Peter told Marissa all along. Marissa uses Peter's soy allergy to her advantage. After she eats the soy appetizer at Colin's funeral, she kisses him.
Peter tries to reach for his EpiPen, only to find it has expired, and the emergency kit in his car is also not there, both actions done by Marissa. This causes Peter to die, even before the paramedics arrive at the scene.
Lacy, talking of his character's ending, added:
"That's just fun, I suppose, at the end because it's the most dramatic thing there is. Birth and death."
All Her Fault is streaming on Apple TV and Peacock.