Miley Cyrus -- Cops Looking for a Guy in Skinny Jeans

Cops now have a description of the guy who abandoned Miley Cyrus' stolen Maserati ... and TMZ has learned the perp has serious hipster tendencies.

According to a witness who spotted Miley's car and reported it to cops ... the Maserati was dropped off in Simi Valley Friday night by a white male in his early 20s, wearing a pair of skinny jeans and a t-shirt.

The witness tells TMZ the guy then jumped into the passenger seat of another car and drove off.

The car sat there all weekend, our witness says, before cops picked it up Monday afternoon after getting calls from a few different neighbors.

We asked the witness if he wants a reward from Miley for helping find her car -- and he said no thanks ... he's not a Miley fan.