Hilton was supposed to be arraigned Tuesday but we're told he simply refused to come out of his jail cell, so he never made it on the bus from County Jail to court.
Turns out ... if he refuses to come out there's nothing Sheriff's deputies -- who control the jail -- can do short of getting a court order allowing them to physically remove him from his cell and take him to the courtroom.
Hilton was arrested after allegedly stealing a Bentley from Rick Salomon's home, driving it to his ex-girlfriend's house and trying to break in. The ex-GF has a restraining order ... Hilton was arrested for violating that order.
TMZ broke the story, Conrad's attorney and family are trying to get him hospitalized as a condition of bail.
The arraignment was rescheduled for Wednesday.