There isn't a single perfect opposite for "discovery" as an abstract noun. It depends on the context. Here are a few possibilities, each with a different nuance:

* Concealment: This directly opposes the act of bringing something to light.

* Ignorance: This refers to a lack of knowledge or understanding, which is the opposite of the insight gained through discovery.

* Loss: This emphasizes the absence of something that was previously known or available.

* Obscurity: This refers to something being hidden or unknown, contrasting with the clarity brought by discovery.

* Stagnation: This implies a lack of progress or change, the opposite of the dynamic nature of discovery.

The best opposite will depend on the specific meaning you want to convey.