At about 21:46 (9:46pm german timezone) I put a [url="https://nevergrind.com/wiki/index.php?title=Lamentation_Blade"]Lamentation Blade[/url]. Then I closed the bank and reopened it, and the Blade was gone.
The Blade was achieved about 3 minutes before that.

Chrome Version 43.0.2357.130 m
Windows 7
Character: Akuma

This was reported ingame by another player that lost a few items this way, his name was Anhagath

Had an unexpected bug appear. Load up and let me know how it looks. No game data was loading properly.

Everything is back! I knew I had more stuff in there.

Also: Please have some forced cache clear on the "Maintenance" Page, as I reloaded a few times and still had the Maintenance-Screen, only after deleting the Site-Cache (CTRL+F5) I was able to login again.

Thanks !

edit: Well... one thing is missing... the "Lamentation Blade" is gone, I put that into the first slot on the upper left side on Page 1. Can't find it in my inventory or bank.

You sure? It was down for a while... had some wife aggro. lol

Yup very sure. I reloaded mulitple times after reading your post.

And added an edit to my answer.

Sorry about the lamentation blade. I don't have a simple way to restore items without it taking a lot of time, so I apologize for that. I think in the future I'll have a command line ability to restore items. That would be nice.