How Do I View Old Toast Notifications?

In some phones you can access the notification log with a simple trick. With others you'll need a custom launcher to do this. What phone do you have? Just in case you could try this. Long press on the home screen, tap on widgets, scroll down until you find settings, tap & hold on it and drag it to your screen, select notification log from that list.
 
It's kinda hidden and depending on your Launcher this may vary, but if you long press on a blank space on your Home Screen and add a Settings Shortcut (in some launchers this may be in the Widget Section, in some others, like Nova, it may be a special 'activity' item). From there, select NOTIFICATION LOG. Voilá!
 
JavierP beat me to it hahaha. But this confirms that it works haha. There are also several 3rd party apps from the Play Store that do similar things (as to whether they just access the Notification Log or if they keep a more detailed log of their own, depends on each app) if you search for NOTIFICATION HISTORY.
 
JavierP beat me to it hahaha. But this confirms that it works haha. There are also several 3rd party apps from the Play Store that do similar things (as to whether they just access the Notification Log or if they keep a more detailed log of their own, depends on each app) if you search for NOTIFICATION HISTORY.

LOL. Yeah, it works. I think with Samsung devices you need a custom launcher.