Why is my deleted photo still appearing in my post or message?

If you deleted the photo from your album, it was indeed deleted.

However, please note that all browsers keep a copy of the image to prevent having to download it next time you open the page containing that image.

This means that your browser, or someone else's browser, hasn't queried SW to check if the image has changed or has been deleted. This is why the image is still appearing for you or someone else.

Eventually, when the browser expires that local copy of the image, it will try to get the image again from the SW servers, and it will show as deleted.

People who haven't seen the picture while it was available, will not ever be able to view it anymore.