Hey all! I had the same experience - here's what I did to re-download the songs:
First I figured out which songs I had deleted by noticing certain albums were missing tracks. I also tried to think about which playlists I edit a lot and what would be on them...
To re-download them, I had to search for the songs individually in the ITunes Store app on my phone. Once they showed up in search , I clicked the little price and authorized payment. Then I got a "you already bought this, click here to download again" message and downloaded from there!
Note that I could NOT re-download them from my purchases list or from finding the whole album in the ITunes Store! Only via searching for individual songs in the ITunes Store šµāš«šµāš« definitely some BS.
Anyways I hope this helps!