Phantom oil leak

OK, Ihad an oil leak, quite bad, thatsuddnely turned up (i did increase the idle speed, but that is all It was leaving lines onthe road, and i lost allmost all of the oil in 4 5minute rips (to thetrainstationand back twice)

So, I degreased it all (which has not been done for ages), thenwent for a drive to see where the leaks was, and it was not there! A little seap from the oil nut, and a couple f drips from some pipe coming from inthe engine somewhere, but no big leak (and yes, there is some oil inthere...i double checked!)

any Ideas? I dont want to decide it is fixed just to have it come backagain!

the only theory i have come up with is that the gasket got wet while I was washing it, and expanded to fill the gaps. Does this sound possible to anyone? Or is there any other reason a spreay with degreaser and a wash could stop an oil leak?

Chuck a bottle of engine stop leak in just to be sure. I love the stuff, keep the old girl running stong.