Sometimes, even though you can connect to the cloud, your xbox/ps3 might fail to retrieve your character.
When this happens, your character slot will be empty. At this point, do not overwrite that slot because your character still exists in the cloud.
What you have to do is go offline and do something else for about 15-45 minutes and then log in.
When you are connected to the cloud and your gallery works etc., go and choose your character via "Choose Character" under the online tab.
If you still cannot retrieve your character or can't connect at all, you'll have to wait longer.
My character has almost disappeared 4 times but this guide will help you to not lose your character permanently.