In reply to elliot.baker:
Maybe it was the last one from a market place seller at that price?
Last year I experienced what I assume was that. An item came up on a general search at a lower than normal price for something I had been looking for so bought it. For some reason just minutes later, can’t remember why now, I wanted to check something on the listing and couldn’t find the listing. Not even with using a stored link from the browser history (came up with page not found).
If I clicked on the item in the order page it linked to another page selling same item, but at usual prices, and not the original listing.
Anyway, item arrived in due course, and so I just assumed that when the last one of the item from that seller was purchased the whole listing automatically just disappears from the whole site.