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.
