Cameron Diaz owes a big fat debt of gratitude to a very persistent homeless woman who tried to return her wallet but got blown off by a fancy restaurant ... but stayed close by 'til cops arrived.
The actress went to dinner Thursday night in Bev Hills at the super exclusive and insanely expensive Matsuhisa. On her way out, Diaz unwittingly dropped her wallet on the street ... cash, credit cards, I.D., the works.
Enter the homeless lady, who saw the wallet on the ground and made the connection that its owner must have dined at Matsuhisa. So, she walked inside -- wallet in hand -- in search of Cameron.
Law enforcement sources tell us someone who works at the restaurant told the homeless lady Cameron had already left ... and that was that.
The homeless woman left the restaurant, but instead of pocketing the loot and running ... she stuck around.
We're told someone called police and told them some homeless woman had Cameron Diaz's wallet. Cops arrived in short order, found the woman, and she was more than happy to turn the wallet over totally intact.
Reward in order?