As a cosigner does the auto loaner have to let you know they repoed the car?

No, the lender is not even required to notify anyone in all states. If you happen to be the person in possession of the vehicle, it is possible, quite likely actually, that the repossession agent will be kind enough to allow you to secure your personal property. Take advantage of this, as the agency is well within their rights to charge youstorage for any property left in the vehicle.