Let me give you an example of the situation where I would like to use this "word/phrase/idiom/expression". A friend of mine who had a laptop for 3 months now accidentally discovers that it is screen-touch enabled when his fingertip brushed against his monitor when he was pointing something to his boss. "Discovered" does seem like a good fit but it sounds pretty dull, at-least in my mind.
I have thought of two phrases: "right under his nose this whole time" and "Eureka Eureka" when I would like to tell this anecdote to someone but I am not sure if it is appropriate in this instance. Also I need alternatives to carry a humorous tone not bothering about if it is a bit exaggerated form.