The drain plug can be a real pain to locate. There is only one and the chances of it landing where you can see it by bumping the engine are slim. Try rolling the engine over by hand using a socket on the crank bolt. By turning over slowly by hand you will be able to find the plug.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.