To apply for a replacement you need to report this to the police immediately because you need a police report of the lost card. On the website of the IND you can find the application form to apply for a replacement of your card:
The application costs € 139. If the document has been stolen and you have student insurance you can claim these costs. Please contact your insurance company for more information about that.
Before you leave the Netherlands you have to arrange several things. For example, deregistration with the municipality and handing in your residence document.