You're right, thanks.
That's because I had the spellilng as 'Poroto' and the builder's name with only one 't'... then it doesn't show up on a search.
I also searched for 'Peter' and 'Porsche Special' (as I had the builder as Otto's son Peter, but maybe that's wrong).
Anycase since it's quite a recent puzzle I'm going to have to merge it without points; sorry.