He may have traveled there, perched on someone's pants leg. Unless you're no bigger than a fly, a frog generally won't hurt you. I used to catch and play with them, as a child.
in one of our previous houses, we had a problem with mice in our attic. One day, they just 'went away.' Some time later, DH found a quite large (shed) snake skin, up there. We never saw the snake but were thankful for his/her help.
