I’ve experienced the same thing, this has happened twice now but this time I lost two legendary items. Though I’m lower level and they would get replaced anyway, it still stung a bit more.
It would be great if they could fix this and let you recover somehow.
This happened at the Forsaken mine in Estuar, oddly enough I went back and the mine said it was cleared (green check), so it kept my “progress” but just kept my loot and booted me back to town.