Let us turn the tables around here, let us say a few hundred Mercedes cars where stolen from the German streets and smuggled out of Germany to Egypt and sold at a nice discount in Cairo. I don't think the Germans would mind. They are keeping Nefertiti and saying it is legal, so this would be cool with them.
About this excuse of the bust being too fragile and not being able to move it, the Germans allegedly built the safest cars in the world being able to withstand collisions of 100 km per hour or more. I'm sure your engineers can put the Nefertiti statue inside one of those cars and ship it over to Egypt with an apology for not returning it sooner.