stew laws

hi guys new in here as was previously on a mitsui, for all my sins!!
Have a 2001 discovery, auto td5, looking underneath i discovered a bolt missing (threaded ) on the bell housing which i took to be the gearbox!? panicing now as dont want to think im running a dry.... its almost like a drain plug, square plate below 2-3 " away, retained by 4 small bolts....... am i barking up the wrong tree or is this a breather or just a threaded blank? thanks for any replys.......

That sounds like it is your bellhousing drain hole. The idea is that IF any oil leaks through the rear engine oil seal it doesn't get trapped in the bellhousing and muck up your clutch.

Only block off when wading through water