He crept beneath a bean bag chair at the daycare centre to hide, according to West Jordan police who later reviewed security camera footage from that day. An employee of the centre, seemingly unaware of Leonardo's whereabouts, then sat on top of the chair.
Why the employee did not notice Leonardo, or the child' s apparent absence from the room, is unclear.
"I'm just confused," Sanchez said to NBC affiliate KSL. "I'm so confused on how you don't know where my kid is. How do you not feel him? How do you not hear him scream?"
She said that police told her that, for several minutes, the employee sat on the chair and read to other children.
Sergeant Joe Monson, with the West Jordan police, called the incident a tragic accident. Police say Leonardo was under the chair for up to 15 minutes before the daycare centre noticed he was missing. He suffocated beneath the chair and was discovered unconscious.
Responders attempted to resuscitate the toddler at the daycare, the Saint Louis Tribune reported. He was pronounced dead at Salt Lake City's Primary Children's Hospital later that day.
On Saturday, Dan Sanchez, the boy's father, told KUTV that the daycare needed to change its practices and be held accountable.
"We regret deeply the tragic death of a young toddler at our day care facility. No words adequately describe the depth of the sorrow we feel. And, of course, we do not pretend to understand how devastating this is for the family," West Jordan Child Centre said in a statement through its lawyer Barry Johnson.
As Johnson told KSL: "We know the family well, we grieve with them, and we pray that God will provide them the comfort and peace they inevitably will need."
The daycare centre had two violations in the previous five years, according to a spokesman for the Utah Department of Health's childcare licensing programme; in one instance, children were left unsupervised. The department is investigating the circumstances of Leonardo's death.
No charges had been filed against the unnamed employee. West Jordan officials were unable to respond to a request for comment.