Variously known as a River Anchor or Columbia River Anchor. There is a take fold down model that will stow well and it should be good for rock and rocky river bottoms.

I won't use the buoy lift system, just the collapsible river anchor. The anchor in the pic is not collapsible.

You can, however, see the chain attaches in an eye at the heel of the anchor and is held to shank at the top by a zip tie. Thus if you cannot retrieve the anchor you can break the zip tie with pulling sideways and pull the anchor up backwards. It works, I've lain to a river anchor in some pretty good winds and currents. It's a specialty anchor...for just the right time.