It was this one (cc /u/dontdonk), and it was the last one left. I've noticed with (luxury) watches that 90% of the time, the item is stocked by a third party. Once in a while, Amazon will get a couple and sell them. Obviously the third party items aren't eligible for the prime day sale. There are a number of other new Omega mechanicals available, but the pricing doesn't seem as advantageous.

As /u/mtd14 mentioned, there are a bunch of warehouse deals, but just double check w/ other shops to make sure you're getting a deal