No matter how much a game prepares for its release period, it's almost impossible to achieve that smooth/flawless launch. Though Lost Ark can be in top shape in terms of gameplay, its servers struggled to keep up with the huge influx of players, causing the developer to lock some of the servers.
Getting into a crowded server will be a challenge of its own, and there have also been players reporting their characters missing. The issue generally gets noticed when players can't find their characters on the server where they first created them during their second login.
Before you call the authorities, you may want to check all the servers in the game. If you were trying to create a character in one of the most populated servers, your character could be automatically created in a less crowded server instead. When this is the case, players mistake their characters as gone. Go through all the servers that are close to you to ensure you aren't just trying to log into a server that doesn't host your character.
If you can't find your character in any of the servers, then it could have actually disappeared. Moderators acknowledged the issueand the current recommended fix for it is to verify the integrity of the game files on Steam. If your character doesn't return home after confirming your game files, you should immediately submit a support ticket since you might be dealing with a database problem that the developers can only solve.