1. I sell my items in the action and i get the mail for it, and it shows that the gold will come in a hour.
2. I wait for 8 hours and still get no gold for it. Okay lets give it a chance and wait for tomorrow.
Next day comes and all the gold pending mails are gone and i didn't get any of the gold.
In total it is like 600 gold lost.
Highly unlikely. Pending mail does disappear (thank god) but not all of it sadly. I'm yet to not receive all of my gold and I've sold a ton of crap.
If you do have some better evidence then open up a bug report and explain the issue. Items/gold lost can not be restored unless bought for coins.