At 10 AM your smartphone, using a highly reliable GPS network, tells you that there is a traffic jam on the way to work and advises another route, which you take.
You do not check your phone while driving, and do not see that at 10:01 AM your phone is now reporting normal traffic conditions along your usual route. In fact, however, the original information was totally accurate. There is a traffic jam. The subsequent revision is due to a very rare data processing error.
Evaluate the following assertion: In this case you do not know that there is a traffic jam. Even though the source is highly reliable, you are just lucky that you did not check it after 10:01 AM and end up with a false belief.