Oh, I'm sure they donated them to museums all over the world and sold the others for scrap. They did this to the Lowe and Maus. GOD knows how they managed to do this with the P-1000 Ratte.
First off, the P-1000 Ratte would've needed a catapult the size of the Bismark just to get it to go somewhere, and it would've been too heavy, with the catapult not having enough leverage.