Jason Oppenheim had his sick six-figure luxury car stolen ... and adding insult to injury, his whip got nabbed while at his work's parking lot!

Jason held an event alongside Rick Caruso at the Oppenheim office in West Hollywood on Thursday night for CA Governor candidate Matt Mahan ... where he revealed his $500K Rolls Royce was stolen just a couple weeks ago.

Law enforcement tells TMZ ... a report was filed for the stolen half-a-mill vehicle on March 16 ... and so far, they got nada -- no car and no suspects.

Sources tell us … Jason was at work for the day, and when he was done, he went to the parking lot -- and realized the car was gone. GULP!

Jason has plenty of other amazing cars to get around town -- but still, he wants his RR back ASAP!