Our guild master's account was hacked just before the holidays and our guild bank looted. As for items being restored - it seems to be kind of arbitrary. We got random green and blue boe armor pieces and various other items, but most crafting materials were not restored. Our most significant loss being our cache of hearts of darkness which is a fairly substantial loss for a guild on Mother's doorstep. What exactly was the person responsible for this ticket thinking?
We did eventually get our hearts back after petitioning for them specifically and were able to continue with our progression in BT. We could probably have every item restored if we were willing to go to the trouble of petitioning for all of them.
Upon learning of our guild bank mishap, I researched experiences other guilds have had with hacking/bank looting and learned that if a vault has limited daily withdrawals per character and an officer's account is hacked, the hacker will likely create a multitude of level 1's, ginvite them and max withdraw from the bank until it is completely looted. This will make restoration of the bank far more complicated than if just one character with unlimited withdrawal rights had depleted the bank and will be much less likely to be restored. So while it is a good idea to restrict access to some parts of your guild bank; it is not a good idea to set a daily withdrawal limit.