Authorities tell the Contra Costa Times that 26-year-old Jermaine Grosse was arrested Monday on suspicion of auto theft and forgery.
Grosse had been sent to the county's regional medical center on an involuntary psychiatric hold.
After his release Sunday morning, he shared a taxi with a woman who was going to a San Pablo hospital.
Authorities say when they arrived, Grosse asked the driver to help with the woman's luggage, then drove away in the yellow minivan.
Grosse was arrested after a DMV worker in El Cerrito reported someone was using forged documents to register the cab.
Information from: Contra Costa Times