I would ask Winnie to help me.
Since we wouldn't be able to hear each other through the door when it was closed, we would prearrange a code.
She would flip the first switch on and off once. Then she would switch the second switch on and off twice. Then she would switch the third switch on and off three times.
Then by the number of times the lightbulb came on, I would know which switch she was using which worked.
And I would get to meet Winnie.
So that's my answer to the riddle.