WowAce

Whenever a bid or buyout attempt results in an error message, such as "There is already a higher bid on that item", or "You did not meet the minimum bid", AuctionLite will color the entry as if the bid/buy had gone through. Searching for the same item again will show the listings in the proper state. I believe you can detect these error messages by registering for the "UI_ERROR_MESSAGE" event.

Additionally, when a listing has the bid and buyout set to the same amount, bidding on the item will cause it to be purchased, but AuctionLite will still list it in the list until you search again. You already catch and consolidate the purchase messages in your buyout routine, so I imagine you already know how to detect them.