You can regenerate your static content by running the following command
php bin/magento setup:static-content:deploy
This is the command you'd run before deploying to production mode. If you're running in default or developer mode, those files should be generating for your automatically. My guess is you accidentally removed a folder Magento expects to be there -- running
setup:static-content:deploy may restore that folder, or may result in an explicit error about the missing folders. If it's the later, the error should (hopefully!) provide enough information to rebuild the missing directories. You may want to run the command in verbose mode
php bin/magento -vvv setup:static-content:deploy
This will tell the
bin/magento command to output the actual exception if there's an error.