Removing an old phone number from Messages on Mac

I’ve been having this persistent problem of an old contact number showing up when sending a text message using Messages on the Mac. The problematic old phone number never showed up when sending messages on the iPhone or iOS devices. I tried deleting the cache files on the mac to no avail. (I don’t recommend doing it, as it caused issues with syncing messages.) The old contact kept coming back. It turns out that there can be such things as orphaned contacts. This is what fixed it for me:

1. Open the Messages app and type the old name in the search bar.
2. Select the contact that appears to start a new conversation.
3. Click the drop arrow next to the “To:” field at the top and choose “Add to Contacts.”
4. Delete the conversation.
5. Open the Contacts app and search for the old name or number.
6. Delete the empty contact.

Voila, that phone number from 10 years ago is finally gone!