Joe has a Samsung Galaxy S10 and recently his contacts "came unglued" while text messaging. He couldn't see who he was texting in the middle of the conversation. Leo says that Samsung has its own apps for messaging, plus the Google versions. Leo would recommend replacing Samsung messages with Android Messages. That'll make it less confusing.
It's possible that Samsung's app checked the Samsung contact manager and as such, it could have lost contact. So first, make sure the contacts are all there. Samsung is deprecating some features in accounts and it's possible that the Samsung contacts app may have disconnected from the cloud since it's closing down its Cloud service. So use Google Contacts instead.
But he looked at Google contacts, and all his contacts have disappeared as well. Leo says that when Joe turned on sync with Samsung contacts, it wiped out his contacts in favor of the smaller contact list. So Joe will now have to rebuild his contact list. Then always backup. He can export from Google contacts and make a backup.