This is actually pretty easy to demonstrate though. You can laugh at your own expectations failing when you're alone, as per the phone example. So we KNOW this can happen.

Now, let's change the expectation, and we can see clearly that the laughter will change or disappear. For example, when I look at Da Vinci's notebook, who I obviously think of as an amazing artist, I don't laugh the least bit at the quality of the drawings contained within, and no one that I know of looks at Da Vinci's notebooks and the amazing quality of his thought as a source of comedy. The different aspect that creates the humor in the case is your own expectations turning out to be wrong.

We know this can cause humor by itself, and we know it's here in this case, so the theory addresses it quite clearly and it seems very well defined as laughter at the self.

Here's one more piece of information that strongly indicates this...

https://www.youtube.com/watch?v=ww2d_o0N62w

Here, Michael Jordan, in his mid-30's, dunks on a center, and it makes the commentator laugh. Notice what he says..."Excuse me! I'm sorry!" In other words, apologizing for his own statement or belief that Jordan was no longer capable of that. He's laughing at how wrong he himself just turned out to be.

(having said that, there is a separate emotional reaction that's triggered when someone's ability surpasses expectations, which I have as a solution to another classic "mystery" of human behavior, but that's for another topic)