Hayden Panettiere -- Victim of a Jewelry Heist

TMZ has learned Hayden Panettiere's Los Angeles home was burglarized last week -- and thousands of dollars worth of jewelry was stolen.

Law enforcement sources say Hayden returned from vacation on April 15th and discovered around $15,000 worth of jewelry was missing.

We're told there were no forced signs of entry -- and sources say there were several people who were in and out of the house while she was gone.