The troubled singer, 26, checked out of UCLA Medical Center yesterday afternoon after doctors said she didn't pose a threat to herself or others.
But her family are so worried she didn't complete her 5150 14-day psychiatric hold, they've decided to track her down.
Jamie arrived at the hotel at 9pm and showed staff what appeared to be legal documents.
Gossip columnist Perez Hilton's sources reckon he is likely to have asked them for cooperation.
About 20 minutes later, police arrived and Jamie went into Brit's hotel room - where she was holed up with paparazzo boyfriend Adnan Ghalib, 35 - to get her.
She is now said to be at her home with both parents.
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