A song I purchased is not showing on purchases songs anymore

Back in 2015 I bought a song on iTunes and now I'm trying to download this song again, and it's simply not showing on my purchased songs on iTunes anymore, although it does show on my "purchase history" along with the receipt. I tried downloading on iTunes on my computer and it doesn't show as purchased either. So what do I do?! Am I going to have to buy again a song I already paid for?