Lowther was optioned to Triple-A Norfolk on Thursday, Roch Kubatko of MASNSports.com reports.
Lowther was called up by the Orioles on Friday, and he made two relief appearances during his time in the majors. He allowed one run on two hits and two walks while striking out four in three innings, but he'll now head back to the Triple-A club after right-hander Shaun Anderson was recalled in a corresponding move.