If you don't use the browser, there's no history for that day. Also, some software automatically clears history, cache, cookies, and other things after a set amount of time. The most common software that does this is IO-bit's Advanced System Care, but there are many other softwares that do it. Also, make sure Firefox is not set to only keep certain amounts of history.

Firefox Settings > Privacy. About the middle of the page is the label; History. Next to Firefox will, select; Use custom settings for history.

Deselect Always use private if it is on.
Select Remember browser / download history.

If you want, you can decide how the other setting should be.

If you want, select; Clear history when Firefox closes. Then, press the Settings button on the far right. Then choose what is removed. You can set this up as you wish. On mine, I only have the clear cache option on.