You probably do not need a new license. Simply deactivate the one for your stolen laptop. Unless you have reached the four-installation limit, you can install MATLAB on your new machine without problems.
If you have reached the four-license limit or you simply want to deprive whoever has your laptop from using MATLAB, from The MathWorks home page, click on My Account (upper right corner near your name), then Manage Licenses on the My Account menu on the left, then the Activation and Installation tab.
Open the Windows Command Window (I only know this for Windows) and type vol at the prompt to get your Volume Serial Number. Write it down, since copy-paste doesn’t work with that application. Do this for every computer you have MATLAB installed on.
Back to the Activation and Installation tab, click on the Activation Label for your stolen laptop (the one that doesn’t match any on your list) and deactivate that installation.
