Remove one of a kind item when sold

url of the page with the problem -- : http:/www.atozalpacas.com

I have my settings to Update the product stock on confirmed status set to yes, and sometimes it works an other times it doesn't.
I sell one of a kind skeins of yarn and the site is allowing people to add to cart checkout pay and then come back and purchase again. When I set it up and tested it, the item would go to 0 quantity and then not show anymore but now it doesn't update the quantity and still shows as available.
Please help! I'm getting a lot of frustrated customers right now.

There is no difference between the products.. they are all one of a kind items so I have quantity set to 1
For a long time it was working flawlessly, as soon as an item was purchased it was automatically removed from the site,
but now I have to go in manually to remove them after they are sold. I wonder if I changed a setting along the way but I've looked everything over and it all seems right.
Is it just the one setting "Update the product stock on confirmed status set to yes" or is there another that I should check.
Thank-you for your help, it is greatly appreciated!

Oh and yes the orders are confirmed.. payment received.