Are there a lot of the particular exact item you are buying being offered? Are you buying because although the items are identical, you like the price better?
Then you are probably buying from a dropshipper.
Every one of those identical items and listings is from the same catalogue. Same pictures, same descriptions.
And when the supplier runs out, the sellers, all of them, run out at the same time.
Usually because after accepting your payment, they are told the item is not available.
When ordering, it is useful to read the negative and neutral feedback for patterns of non-delivery, poor packaging, or low quality.
While some buyers don't even want to be satisfied, and feedback is a mediocre measure of customer satisfaction, pattern showing a problem should be heeded.