That's what happened Thursday just north of Washington, police say.
"Dad forgot baby was in the car, parked the car, got on the Metro," said Lucille Baur, a spokeswoman for the Montgomery County, Md., Police Department.
"I don't know exactly when he got the memory flash, but he was in D.C. when it was the horrible defining moment, 'Oh my goodness, I think I've left my child back in my car,'" Baur said.
At that point, she said, Jonathan Sander got off the southbound train and onto a northbound one, returning to the Shady Grove Metrorail station about 12 miles north of Washington
By that time, other commuters had noticed the 7 1/2-month-old girl in the back seat of the car, firefighters had opened the locked door and the child had been taken to a hospital as a precaution.
She was reunited there with her mother.
"Child Protective Services was comfortable with releasing the child back to the mom," said Baur. "We all believe that the child was not intentionally left in the car."
Sander, described as "terrified, embarrassed," was charged with leaving a child under 8 unattended in a car or building. He could face a fine of up to $500 and 30 days in jail.
A call to Sander's home was not returned.
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Negligant parents like this guy outta be smacked a few hard times in the head. I know people can get caught up in rush hr, but do idiots like these have to wear a post it to remember they're baby. I think that would fit the crime to make him wear a post-it.