SLC can't tell me what my loan was for

I started university in 2006 and graduated in 2011, this cost me £26,000 in maintenance and loans from SLC (before interest), a figure I've always thought was a bit high.

Unfortunately, being a bit naive at the time I didn't keep all of my paperwork from the SLC and although some of it is available electronically on their website its missing quite a bit.

I decided to ring them up and see if they can give me a breakdown of whats what, but they can't. What they can tell me is they've paid me for at least one semester for a course I never enrolled on, and they've given me the dates of payments with a high level description and an amount but its not enough to identify what its for.

They tell me the rest of the paperwork has been misplaced when they moved from a paper based system to an electronic one. This kind of puts me in a difficult position, as I'm conscious I could be paying off a mountain of debt that I don't actually owe.

Has anyone had a similar experience with the SLC and if so what did you do about it?