Santander no longer have any record of my first mortgage

I've very recently placed all of my pension funds in to one basically to keep things nice and easy for the wife if the unthinkable happens. Since my first mortgage back in 1992 where it was attached to my pension I've always kept tabs on every policy and kept all the paperwork. I contracted out and then back in to serps which created further policies and then my then employer changed companies 4 times in 20 years...creating the remaining policies.

Abount 2 months ago a letter from Royal London dropped on the mat telling me about a pension I had no idea about and was apparently not paid in to since 1998. Back then Royal London was owned by Abbey National But they advised me to contact Royal London as they had apparently no connection anymore.
I then phoned RL who were literally of no help what so ever who then directed me back to Santander (Abbey) who were the ones that set the policy up.
It went like this for about a week when I eventually managed to speak to someone that actually gave a toss. My question was where did this policy come from, why had I not received documentation since 1998 ( I was told this by Royal London who could see that only)
Things started moving when I was told that the only way to take this forward was to raise a complaint, which of course I did in early December.
They took all my details, addresses for the past 30 years, account numbers of mortgages etc and told to expect contact in a few weeks.
Just before xmas I got a call from Santander advising me that they were looking in to the unknown pension but aswell were investaigating mis-sold pension based mortgages which I was advised back in 1992 which I never made any mention of.
Filled out further forms asking me what I remembered ( back from 1992-1995) and how it was sold to me and sent it all back.

Early part of this week Santander phoned with an update and advised they weren't able to find my first mortgage which we took out in 1992 and then added a further 17k to when me moved in 1995.
literally no record of it anywhere.
They seem so hell bent on investigating a mid-sold pension mortgage theyre not actually investigating why I had a pension I knew naff all about.

it seems to me that perhaps mis-sold mortgages will be the next big thing but why the fing hell have they no record of my first mortgage?

Do they have to keep such records?

Santander are really bad at all things financial.

Just had a similar to do with Aviva (took over Friend Provident). I had an endowment policy linked to an Abbey mortgage taken out in 1991. It had matured and I wanted to cash it in. There was a tag to the policy that Santander (formerly Abbey) had an interest. The mortgage was paid off in 1999! Took eight weeks to get the policy cashed due to delays. Aviva blaming Santander and vice versa. Got there in the end, although they still took an extra payment!

It's all bit of a mess due to various buy outs and take overs. Royal London contacted me a few months ago about another life policy I'd forgotten about. They'd taken it in from another company.

Had a similar problem with my bank and PPI, for things that are archived i.e. completed they only have a legal obligation to retain records for 6 years. For this reason if you don't have policy numbers etc. it can be very hard to find anything useful from them.

I'm not a lawyer, just what I was told.