Compositions and recordings exist as 2 separate pieces of copyright. Songtrust administers your composition side, while your distributor (Cd Baby, Distrokid, etc.) or label manages the recording side.
Being that not all songs have recordings, we always register all compositions from your Songtrust account regardless of what (if any) recording info is provided.
Please note that we highly recommend including ISRC's whenever you have them to optimize your royalty collection.
Here is information regarding why adding ISRC's is important if you do have recordings out there.