I am not aware of any VIN sticker on the front bumper, at least of a facelift E500. My car has its stock bumper and trust me, I've been very up close and personal with it in recent weeks. Never seen a VIN sticker on it.
The REAR bumper of .036 models have a VIN sticker. It is on the underside of the edge of the bumper, and can be seen by getting on the ground and loooking directly upward.