Spoke showing signs of stress at the elbow, but not yet broken.
This spoke was an inbound spoke on the non-drive side of a disk-braked wheel. The disk brake vibrated and screeched when applied hard. I believe this caused the inbound NDS spokes to momentarily go slack when the brake was vibrating. The pattern embossed on the inside of the elbow is from the spoke hole in the hub. The edge of this hole would be the location of a crack initiation, leading to spoke breakage.