Rockstar has warned GTA Online players that it's possible to accidentally delete their characters, but have at least come up with a common sense solution. "Don't do it," basically.
This issue arises when server issues causes players to see a blank list of character slots, even though they've created one. Some players try to select the first seemingly empty slot, but doing so effectively overwrites their existing character along with all of their progress. Here's what Rockstar support has to say on the matter via a recent update:
If you have previously created a character but see an empty character selection screen when entering GTA Online, please back out to GTAV Story Mode and try re-entering GTA Online through the pause menu (repeat or wait until Rockstar cloud servers are back up). Do not create a new character in the empty slot where your character should be.
If you receive the message 'The Rockstar Cloud Servers Are Unavailable', please return to GTAV Story Mode and follow the steps above. Please do not press “Retry” on the message and do not proceed online with saving disabled, as this may lead to overwriting your existing character.
We apologize for this inconvenience and are working on a permanent fix for these issues.
This is just part of a larger set of problems that has seen GTA Online players losing hours of progress due to inconsistent cloud saving on Rockstar's servers. Exercise caution.
Matt and Carl have been logging some time with GTA V's fun yet buggy multiplayer suite, and masses of videos are on their way. Apparently Matt's a bit of a mercenary to say the least.