The foam will make it's way into the cylinders, past the piston rings and end up spewing out anywhere it can. Some idiot overfilled my motorcycle, funny thing is the capacity is printed right over the filling spout. Long story short riding it home I stopped at a light and found myself standing in a rising cloud of thick smoke, and the bike cut off. The oil had poured out around the headgasket and covered the engine. I fixed the problem, and degreased the engine, but there was oil all down the exhaust and in every nook, so it took a day to burn it all off.
It would make sense that your oil has still not all burned off, it only takes a little, and some parts of your engine dont heat up enough to smoke it all off at once. But do check where you can for any gasket/seal problems. Every overfill is different, some engines just quit, some build up so much pressure that they blow gaskets.