"That was our best lead," Nestel said Friday. "That was the most likely item that was going to help us solve this."
Philadelphia police identified the suspect as William Clark, 37, of Philadelphia; he faces charges of aggravated assault, theft and related counts.
Clark was arraigned overnight and is being held on $2 million bail.
Clark was arrested around 2:30 p.m. Thursday at a plaza near City Hall, authorities said. A SEPTA officer identified him because he was wearing the same jacket, Nestel said, which was visible under another jacket. He resisted but was arrested and the victim's cellphone was recovered, police said.
It doesn't appear the suspect knew the victim and investigators believe he may have mental health issues, Nestel said. It wasn't immediately known if he had an attorney.