How do I unhide the top menu bar on my desktop?

Upon further examination, the menu bar only hides after Safari is launched and it is not in full screen mode. I had my system on all day with Safari running the entire time. The top menu bar only started hiding at the end of my day. I'm not sure what set it off. I tried closing Safari (at which time the menu bar reappeared) and then relaunched it again but as soon as it opened the menu bar hid itself. Very strange behavior. That seems to be the only application causing the menu bar to hide.

Thank you for your response. Much appreciated.

This problem wound up resolving itself with a very simple solution.

I shut down my system for the day and started it up the next day. I then launched Safari and noticed that the hidden menu bar did not occur. This isolated incident was obviously some type of computer glitch which I'll probably never be able to duplicate.