I lost my old man when I was about 5, saw him here and there until I was 6 and a half maybe 7. Met him last year (then 28) after 21 years.
We didn't get on, we bought up the past too much. Though if I'd have never seen him and then found him, perhaps we'd have gotten on. But hey ho.
Funny thing is, he was still in Stoke on Trent.
So you can find people after so long so keep looking mate. Electoral registers can give you lots of information. And there are people you can pay to search these for you if you don't know how to. A bloke offered my Dad's address to me for £50 but I found him before committing. I found that bloke after searching for "missing person finder" or something like that on Google.
I hope you find him soon though mate. It's lovely meeting up for the first time ever (felt like that to me as I couldn't remember much of my old man. And it felt like that to him as he was expecting a 5 year old to appear in some sense - the last memory he had) and we had a right laugh most of the time. Obviously you'll have none of the sour feelings there at all so hopefully that buss will last forever then.