Go to contacts.google.com on your computer browser. Do you see your contacts there? (Make sure you're signed into your Google account on the browser.) If not, then at least we can say they weren't synced to your Google account.
If you entered all of the contacts into your phone using its "Phone Account," rather than your Google account or Samsung account, and you never manually backed up the contacts anywhere, then they're at risk for being completely lost if something happens to the phone. That's why it's always a good idea to sync your contacts to one of these clouds.