Hello, lately I've had some issues with selling an itemon Auction House, which has disappeared when it was still pending.
Once it was a server restart and then following morning like 20 stacks of sold ores were not in the mail (cash), and today I've sold a titantsteel bar and when checking the mail it said that sale is pending for 2 more minutes and then there was nothing in the mail and no cash gained in my backpack...
I think this can happen if a crash or restart has any rollback after server comes back up. Rollback can cause a lot of weird problems, for instance I got an achievement that gave a reward in the mail, but right after I got it the server crashed and there was rollback. After the server came back up I had to complete the last part of the achievement again, but when I checked my mail for the reward...there was 2 mails and 2 rewards. The problem is that after rollbacks the server only remembers some things but not everything, and mail especially can get messed up like this. If you have a sale pending, you can get screwed out of that gold.