Two voids were discovered - and the one you mentioned has since been breached and a camera inserted. I'm avoiding the word passageway because the general interpretation is that it seems to be an inspection space or stress relief chamber, as it sits directly above the "actual" entrance to the pyramid.

Video on the subject: https://www.youtube.com/watch?v=49870qW9pQ8

The second void is more exciting, in my option. It is much larger - it is thought to be of similar size of the Grand Gallery, and sits some distance above it.

You do recall correctly!

https://www.nationalgeographic.com/science/article/giza-pyra...

This story? https://www.jst.go.jp/EN/achievements/research/pdf/mitsuhiro...