I complained.
I had a couple of those in my cart and then did about 5 more minutes of shopping to make the order worthwhile. When I went to checkout no more than 10 minutes after putting those in my cart, I got a message that the micrometers were no longer available. I wrote a message to Amazon telling them that would never happen in a brick and mortar store, so I would finish my Christmas season shopping locally cancelling the rest of my order. They just confirmed what I told them and apologized.
In my opinion, their shopping cart is flawed by allowing someone else to remove it from my or anyone's cart because someone beat them to the checkout. It is also in Amazon's best interest to allow some to shop more to maximize sales receipts. My own ecommerce site doesn't allow someone to take an item out of a cart after someone committed it to their shopping cart. My site actually makes the quantity change immediately. But I should probably test it again especially since most of my items are in single quantities.
Steve