Suspicious interracting and purchasing and item from a vendor

Dear Game Master. Writing to express my dissatisfaction of unfair game from a player
The thing is, there is a vendor in Netherstorm who sells Khorium Power Core. Seeing him regularly trading an epic helicopter mount on AH. This makes me think there is something behind it.
Day after day I try to catch the selling item but everytime this player gets it first. Is this kind of a cheat/hack/script or whatever but it makes it so fast that he buys it instantly and everytime he just comes in a right time. Just in the same second that I try to purchase, I get an error saying: the item has been already sold (he purchased it just in a millisecond after I saw the item appeared and I quickly tried to bought it).
Kindly bring your attention to this as it makes kind of unfair for another players, if he uses some kind of a hacks or scripts. If we think of this of how does it affect others ? - the truly bad side of it is speculating the prices on AH using the cheating way of getting items.

Make a ticket with your evidence of him cheating.
But it sounds like you want GMs to "do something" about a player that smarter and faster than you.

3 hours restock time, he probably uses the "interact with target" keybind + a macro to buy it quickly

General item buy macro with pop-up confirmation. Quite easy to make. Then you just login minute or two before the item is in shop again, and spam the macro.