@monicakm did you link to the photo instead of downloading it and posting it here from your computer? If so, it could just be the site. I don't really understand how it works, but sites move their pics around.
Here, you can post as many pics as you want, but on some other social media sites you have to pay to post over a certain number of pics. I have linked to pics in my own Public Google Account and Facebook account on other sites and they show up for awhile and then disappear. The http address remains the same, so it's something else that happens. I just know it happens.