Tricky one you've got there! It is a two second job once you are up there, but 40 feet would be at the outer reaches of my comfort zone on a ladder. I would have no worries about the ladder leaning against the house, but the height would still get to me. Cherry picker would be better, but a lot of expense for that 2 second job.
To my eye you also have something missing from the apex of the barge board, covered by half tiles to right and left but not in the middle - might this be how the wind got under the tile that moved? I'd want to bed the tile on some mortar to hold it in place, so maybe a wee bit longer than two seconds, 40 feet up, bucket of mortar in one hand, trowel in the other, clinging for dear life to the ladder with...