Have you tried using the /devconsole in game to see what the event actually returns or what is returned if anything other than nil in the devconsole ?
You could also just test it out with /run or /script in chat or as a macro.
For example:
/script QueryAuctionItems("Nobles", 0, 0, 0, 0, 0, 0, 0, 0, 0)
Result
Finds anything on the AH with the word 'Nobles' in it.
Hint: AH window has to be open before you click the macro.
" getAll
Download the ENTIRE auction house as one single page. Only allowed when CanSendAuctionQuery() returns true as its second return (~every 15 minutes). May disconnect people with low bandwidth. Also see notes on client-to-server traffic in GetAuctionItemInfo() (Added in 2.3, though initially disabled. Appears to be enabled as of 2.4)"
Can try the
/script canQuery, canQueryAll = CanSendAuctionQuery(); message(canQueryAll);
if this returns true then there should be no reason as to why the
QueryAuctionItems LUA function doesnt work.
I would just suggest playing around with these functions a bit more in /devconsole or as macro/chat commands and see if you cant get a more valid result.
Also when reading into the GetAuctionItemInfo() LUA function it states as such:
"Blizzard's standard auction house view overcomes this problem by reacting to AUCTION_ITEM_LIST_UPDATE and re-querying the items.
However, this event-driven approach does not really work for e.g. scanner engines. There, the correct solution is to re-query items with nil owners for a short time (a low number of seconds). There IS a possibility that it NEVER returns something - this happens when someone puts something up for auction and then deletes his character.
Also note that these GUID-to-name queries cause client-to-server bandwidth; 14 bytes each (in 2.3.2). For a normal 50-item page this is of course negligeable, but for a full-AH scan on a medium-size server, you easily generate enough traffic to disconnect yourself if you do not throttle the rate at which you send queries. See ChatThrottleLib for information on client-to-server bandwidth. "
If you wanted to create some sort of alternative could be possible.