The problem is you have to know the approximate timeframe of your last visit - eg. If it was in the past week it may not be searchable in other categories such as *more than 3 months ago".
... likewise, if you can still find it by going to a currently open tab and hitting"back" enough times, it may not have been addded to history yet.
Firefox's history is a little idiosyncratic. One of the less polished parts of the browser.
Control+Shift+H or you can find the link to it in the history menu in the main Firefox menu. Or at the bottom of the history menu from the history button if you add it to your toolbar. Or in the Library section if you use that menu/button.
The sidebar is a cut down overview.
Same for bookmarks, the full bookmark screen has more depth and features than the sidebar.