Hello fellow players I just wanted to warn you about this bug, of course we will have the GM service but better prevent than be sorry ^^;

As announced on the official FINAL FANTASY XIV Forums, we have identified an issue wherein materia attached to a player’s equipment may get lost when the server goes down for maintenance work. If you notice that your materia is missing after the conclusion of this maintenance, please place a GM call. A GM will conduct an investigation and provide maximum support to restore your materia. You can avoid running into this issue by equipping the item which the materia is attached to or storing it on a retainer before the maintenance starts.

http://lodestone.finalfantasyxiv.com/pl/news/detail?newsId=35a8c7c78209b5a7462c8f7ddf185cc46f79986e