GM's does not restore characters, so you need to find out how and who deleted it.
If you didn't delete it yourself, then you need to review your account security practice. This is your responsibility - and only yours.
- Do you share your account information with anyone? Friend, brother, wife ....
- Is your account name easy to guess? Don't use your forum or character name as account name.
- Is your password easy to guess? At least 10 characters long including numbers.
- Do you download stuff from suspicious sites (which may include keyloggers) ?
Finally, have you checked and doube-checked you are actually logging into the correct realm?