Saved Lot to Bin, Portrait Paintings Missing

Try going into the old save again and first taking all the portraits off the walls and placing them in one of the Sims' personal inventory, and then saving the family and the lot again. I don't even know if this was intended to work this way, but I know that it at least sometimes does. I've used an old active household from my library in a completely different save, and I was pleasantly surprised to find the portraits and still lives one of them painted preserved in her personal inventory.