That is is even still recognizable blows my mind. I mean this looks like it is in the open, on a sloping rock face, exposed to the weather for 12,000 years in the rainforest.

How the hell does it still look that good?

The linked article is from 2020, which seems to be when researchers started publishing more about it, not when it was discovered. Modern re-discovery seems to date back to at least the mid-19th century by Italo-Venezuelan geographer Agostino Codazzi, and then multiple other mentioned people in the 20th century. https://www.discovermagazine.com/amazon-rock-art-could-depict-millennia-old-megafauna-43686 The delay for research to catch up can be explained by the presence in the region of the FARC, the Columbian Marxist–Leninist guerrilla group, which disarmed itself in 2017 after a peace deal and 53 years of activity. https://www.sciencedirect.com/science/article/pii/S0278416524000448#b0130

has been discovered

OP, this discovery is from over four years ago. The Live Science article is from December 2020, and the open-access journal article was published March 2021.

"Colonisation and early peopling of the Colombian Amazon during the Late Pleistocene and the Early Holocene: New evidence from La Serranía La Lindosa" in Quarterly International by Morcote-Ríos et al., March 2021.

Please be careful about phrases like "has been discovered" which imply recency.

Neat!