Accidentally removed vendor folder in laravel project

The Vendor folder is created by running composer install. It contains only the packages which you have asked composer to track in the composer.json file. If you have a composer.phar file in the root of your application run php composer.phar install.

https://getcomposer.org/doc/00-intro.md is probably your best source for additional information.

Just run composer install after cding into the Laravel project's directory.