That mobile has had, to date, six queries on the 'who called me' site - I use this site a lot as have inherited a number which seems to have been sold to every cold calling site in the world!
May have been a former work colleague. I have occasionally tried to locate some of my former colleagues but have done it by email/facebook, but might consider ringing.
You could always ring back and ask I suppose if you are still curious
I hate to admit that strange things like this annoy me. If I can find some sort of explanation on the internet then I am happy. Luckily my brain has a problem retaining information so I eventually forget about whatever it was.