Grant:

Actually there is a weird feature in the GT3/RS where the oil level gauge is reset when the engine cover is opened/closed.  I think because there is really no other reason to open that lid (nothing to see here, move along...), the system checks whether you just added oil.

exactly, so there is a connection between slamming the lid shut and the oil measurement system.  well, i shall drive more tomorrow and see. for now the warning  light is square off while it was on until i slammed the lid. let me just add that restarts did not help.