Word for instantaneous mismatch of expectation and reality

I'm looking for a word to describe the feeling when you think you've reached the bottom of the staircase and there's actually one more step and suddenly you're falling, or when you swing a bat and think you're going to make contact but miss the ball, or think there's another drumbeat coming but there's silence instead. The feeling of your expectation misaligning with reality at a particular instant.

Seems like the kind of thing you might find in the Dictionary of Obscure Sorrows. I'd love to know if there's anything like this or close in English.

Solution 1:

The staircase situation specifically is phantom step.

The mismatch between expectation and reality might be something like cognitive dissonance but I'm not entirely sure. I don't think there is a specific word for the feeling you want to describe.

However, I think any of the following words/phrases would work well:

Caught off balance: To startle one; to come upon one unawares or unprepared. Usually used in the past tense.

Example: The security guard caught the thieves off balance. [TFD]

Startled: If something sudden and unexpected startles you, it surprises and frightens you slightly. [Collins Dictionary]

You could say you were startled.

You could also use caught unawares, dumbfounded or bewildered.

Jarring and incongruous could also work.

False summit: In mountaineering, a false peak or false summit is a peak that appears to be the pinnacle of the mountain but upon reaching, it turns out the summit is higher. False peaks can have significant effects on climbers' psychological states by inducing feelings of dashed hopes or even failure. The term false peak can also be applied to non-mountaineering activities where obstacles posing as the end goal produce the same psychological effects. [Wikipedia]