'Ice Road Truckers' Star Tim Zickuhr -- GUILTY of Prostitute Kidnappi

"Ice Road Truckers" star Tim Zickuhr didn't convince a judge the woman he allegedly tied up and threw in a closet was not a prostitute but a flaky friend, because he was just convicted of kidnapping.

TMZ broke the story ... cops say last April Zickuhr bound a Vegas prostitute named Snow White with backpack straps and locked her in a closet ... then tried to collect a $1,000 ransom from her friend, who happened to be a LVPD cop.

A Nevada judge wasn't buyin' what Zickuhr was selling and found him guilty Tuesday of kidnapping and extortion. The judge then threw the book at him, sentencing him to a maximum of 15 years in prison.

Zickuhr hasn't appeared on the History Channel show since 2011.