hundreds protested an air force vet and former playboy model 's arrest when she tried to stop people from trampling on a flag .
valdosta state university closed after police warned there would be thousands of protesters and as they searched for student eric sheppard .
police said they traced a gun to a protester who was part of the flag-walking demonstration , and issued a warrant for eric sheppard 's arrest .
michelle manhart , 38 , was handcuffed at valdosta state university , georgia .
former usaf training sergeant took flag from campus protesters on friday .
police arrested her for not giving it back because of how it was treated .
manhart posed for raunchy military-themed playboy spread in 2007 .
was demoted from her sergeant rank , and later left the military .