I’m so sorry for your loss. Thunderstorms do suck ;(
We lost a pony this way as well. He was by a stream and was the only one with shoes on so the lightning hit him and not the others around him.
We also lost a 2 year old lab this way. A freak storm popped up when we were at work and he was on a line that was tied from tree to tree so he could be outside and could go in his doghouse. It struck the tree and travelled down the line to his collar. It was a coated wire as well (like a laundry type of line) but it fused all of the metal links inside and you could see how it went down to his collar.