Rest assured, they're almost certainly not lost for good!
Here's how to find them:
Check in the Trash Bin
Make sure you've signed into the right account!
Often times, we see that members originally created an account via one method (like Apple signon), but then try to sign-in via a different one (like Google), inadvertently creating a new account (!).
If you're sure you're in the right account, check your folders
You may have accidentally moved a song into one of them.
Wait a little bit
Sometimes serverside issues can temporarily hide songs; you'll typically see them again in a few minutes or (more rarely) an hour later.
If you're still not finding some or all of your songs, drop us a line (via the messenger icon on the bottom right) with as many details about the missing songs as you can.