A law firm's attempt to cash in on a home-shopping network's failure to pay state use taxes has been rejected by a state appellate court.The 1st District Appellate Court unanimously ruled that discovery in a whistleblower suit filed against QVC by Schad, Diamond & Shedden P.C. was properly limited to a deposition of the network's tax chief, and the firm was not entitled to a cut of the taxes the network eventually began paying.Justice P. Scott Neville Jr. authored the 15-page decision. He was joined by …