De acordo com VFS Global (a empresa que lida com pedidos de Schengen para muitos consulados na Índia):
What do I have to do if I have lost or misplaced my Indian passport with a valid Schengen visa?
You are strongly recommended to keep photocopies of your passport’s data pages and of the Schengen visa. A visa is a valuable document. Inform The Embassy / The Consulate from where your visa was issued immediately if you have lost your passport. You must apply for a new visa by submitting all documents and payment of visa fees. You must submit a copy of the Police First Incident Report (FIR) with your application. It is preferable to also submit a copy of the visa and the lost passport for ready reference of the Visa Officer.
Portanto, a resposta é que você deve solicitar um novo visto com um boletim de ocorrência policial sobre seu passaporte roubado.