where'd my songs go?

I downloaded songs years ago (maybe on my old iphone or even an ipod--can't completely remember) but they're not showing up in my music. When I go to the itunes store app on my iphone to purchase it (again), next to the title it says 'purchased' but it definitely doesn't show up in my music library. I even try to click on 'purchased' maybe to re-download it, but it does nothing. Please help, I miss my old songs!