There have been a few questions here in the forum and in the chat about "disappearing" banners, rotating images, and content on the sidebar and headers. While there are a lot of reasons for why this could happen, there has been a trend.
If you are using Firefox's extension Ad Blocker, or another similar ad blocking add-on for your browser, turn it off and reload the page to check to see if that may be the problem of the disappearing content. The ad blockers work really well, but they aren't perfect.
If they are still "disappeared", then validate your page and start looking for other solutions. But this might be the answer.