I couldn't find any explanation online anywhere, and I see it being used a lot as such an expression "[something] [発見]{はっけん}", like "shield is found." in Apex Legends game for example, and in some anime "いい[棒発見]{ぼうはっけん}", being another example.
Isn't it a noun? How is it being used here on its own, instead of its verb form? Because of its tone I wonder whether it's originally a military expression?