There was a lot of iron ore mining activity in the area and as the loco, which was switching a mine yard, passed over a certain spot the ground subsided under it.
The crew were able to jump clear but the logistics of recovering the loco, which was a fairly elderly 0-6-0, proved too much for the Furness Railway so they just left it where it was and filled the hole with spoil.
Every so often it's suggested that at attempt at recovery is made but the general concensus is that it will have sunk into deeper mine workings so there, I suspect, it will stay.
There are also a number of British "8F" class loco's at the bottom of the Bristol Channel. They were being shipped to Europe as deck cargo to help with war reparations after 1945 when the ship they were aboard was caught in a violent storm.
The captain had no choice but to cut them loose in order to lower the centre of gravity on the ship and save it.
