This just happened to me as well. I purchased an item on the AH but it did not show up in my completed tab. My gold was taken though and the transaction log lists it as complete.
I submitted a ticket with the transaction number and got an email right away saying that the item delivery could take up to 24 hours.
Just curious, did you get your item yet?
My case is a bit different from what I have heard from others.
What I have heard is that some people have experienced transaction delays. They purchase the item but it does not show up in the completed tab. Usually after 24 hours has passed the item magically appears and the player can send it to their stash and start using it.
In my case I purchased the item. The transaction went through sucessfully. I went to my completed tab and saw the item ready to be sent to my inventory. I clicked the item. Sent it to my inventory. Upon resuming my game the item was not present in any of my inventory tabs.
I checked each tab 3 times and scanned each item carefully. Could not find the item I had purchased. I left the game. Went to my completed tab. Saw the item was not present at all in the completed section. Resumed game. Checked all tabs. Still no armor.
I logged out and logged back in multiple times. Checked completed tab. The item shows up as purchased. Checked completed tab. Nothing there as before. Resumed game. Checked all inventory tabs. No item present as before.
I just submitted a ticket. So hopefully ill get a response to my issue.