This feels like a Monday photo to me. I do not understand how that shoe came to be there. So many questions. No answers.
@eclectech no laces and left behind says to me an ankle or foot injury - laces needed to be cut off, and if someone was stretchered or supported off they may not have realised their shoe was left behind.
@eclectech may have been there a while and rain-washed?
@evilstevie Can confirm that it was very wet, so aye, that makes sense too.