For me, npm folder was vanishing after "npm install" of any module.
And this article helped => https://www.reddit.com/r/node/comments/8m0gyg/npm_install_removes_itself_and_some_packages/

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please follow the below steps :

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delete package.json, package-lock.json and node_modules directory first, then run these

npm i -g npm

npm init -y

npm i --save-dev discord.js