As Rockstar continues to investigate the issue of disappearing characters, cars, items, money, etc. in GTA Online, they are continuously providing advice on what to do and not do if you encounter such a bug.
In an update today, the developer warned that you should not create a new character in the event you see an empty slot where your original character should be. Instead, they recommend you back out to GTA 5's Story Mode and try re-entering GTA Online through the pause menu. They suggest repeating this process or waiting until Rockstar cloud servers are back up.
Rockstar also said to return to GTA 5 Story Mode and follow the steps above if you receive the message "The Rockstar Cloud Servers Are Unavailable." They warn against pressing "Retry" on the message and recommend you do not proceed online with saving disabled, as this could lead to overwriting your existing character.
"We apologize for this inconvenience and are working on a permanent fix for these issues," Rockstar said. We'll continue to monitor the situation and provide you with any updates once we learn about them.