I agree with you.
Here is an MSM article that discusses this theory:
Five years later: New theories revealed in baby Lisa Irwin’s disappearance
One tip that became public involved a handyman, John “Jersey Joe” Tanko, who had a criminal record and worked in the neighborhood. He dated Megan Wright, who publicly reported her cell phone was called by one of those missing cell phones.
Wright said many other people had access to her cell phone, and she would not make or receive that call.
Police never named Tanko a suspect and said he cooperated with investigators who were satisfied with his answers.