Using older versions of Outlook for Mac for personal email and calendar
Just an FYI as someone who often has this problem also.
Unfortunately the suggestion doesn't work since after you dismiss something (which happens OFTEN since new reminders take focus away from the one you were about to snooze or dismiss), you have no way of knowing what you just dismissed.
Some items show up in the task list (but not all) and also that only sorts by date, not time.
Some items show up in the calendar but the list view has no modified date at all.
There just doesn't seem to be any way to either prevent Outlook from causing accidental dismissals or finding a task/event/flagged message that has been dismissed. Essentially you just need to remember all your reminders in case you aren't reminded :)