Update - Spoke to my insurance co - (Linea Directa) as they offer free legal advice as part of the motor policy.
Although they could confirm there must be 'some evidence' if you do not have the original documents (permisso and tecnica ficha) - i.e the white slip as Johnzx says... I have got a copy of the appliction at traffico from my appointed representative now. (I am surprized though that he thinks so lightly of having people documents and giving no receipts. NB He is a registered person who deals with Trafico on a daily basis, he just isn't a certified Gestor. He is also well known in our area and comes 'highly recommended.' But as I pointed out to him - would he pay the fine if I was stopped and got the 'wrong officer' on the day...)
He still maintains that it is not the law to have the permisso and techinca ficha (or compulso copies - i.e police, notarty or authorized person who stamps them.)
I disagree with him after asking on several forums, speaking to my insurance co.
I would like help with finding the actual Boletin regarding this matter (so I can show him in Black and White).. I got this far... http://www.boe.es/buscar/boe.php?accion=&id_busqueda=31d6de4c710c1c73ca2903894225f3d3-0-100 but have no clue as to what the latest BOE is on the updates I am looking for. (I don't think I am looking in the wrong place, I just don't know the no of the BOE and it is like trying to find a needle in a haystack!) Any help welcome. (I know there have been a lot of additions to what is 'fineable' in recent months.. but specifically I want to find re the documents. (The last main law was in 2012 when it said it was no longer necessary to carry original insurance do - and proof of payment - but I still do just in case!)
I have been searching under Minesterio de Interior, and Direccion General de Trafico
(Solwayiceman .. I do have a good level of Spanish, however that is not always enough with red tape. I ask for help when I need it. Also I don't want any aggro (have enough stress in my life), so often hire a gestor when I can afford it.)