I remembered reading about one such discovery a while back. I dug up an article (linked below), but after rereading the article, I am not totally sure if the discoveries were directly related to deforestation or the scientists had a hypothesis of people living in a specific area and deforestation helped in their ability to visit the sites to obtain further evidence.

For example, in the source paper, figure 4 shows many of the research sites being located in deforested areas (white). But the paper doesn't specifically say "deforestation helped us".

WP article: https://www.washingtonpost.com/news/speaking-of-science/wp/2018/03/27/archaeologists-discover-81-ancient-settlements-in-the-amazon/

Source paper: https://www.nature.com/articles/s41467-018-03510-7

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I seem to recall another discovery (temple?), but I can't find any info on it. All I remember is something along the lines of "it was 50 feet from us and we never knew it was there" (ie. jungle vegetation hid it extremely well from a nearby village).