It's possible that when you found him the first time he had been released first in the US and then in the UK. The same may happen with this one. Music - as well as some of Apples gadgets - is often released territory by territory and different deals are done in each one. So they may test the artist in the US before they bother releasing in the UK. Different royalty agencies are involved in each country so that's why this happens.
Regarding iTunes, I don't think you have to back up your music before upgrading - I certainly didn't. But if you have a large and treasured collection it might be worth considering in case something should ever happen to your computer. MWHAHAHAHAH! Sorry, that sounds like a threat but it isn't - computers die for no reason, or they get nicked. I think there are some online backup solutions for music now.