RaeA, Lilium longiflorum is supposed to be hardy in zones 5-9, so yours should survive without a problem in zone 6. I have not tried to replant one before, but am giving it a try this year, and will give it a little extra winter protection since I am in zone 5.
I live in zone 5 and a couple years ago my daughter gave me one for an Easter gift. I planted it in my flower bed and last year I had 3 pop up and bloom beautifully. I was really suprised because I didn't realize they grew in my zone.