Technical Cofounder Dropped Abruptly

Hi all,

So I was working on a startup with a technical founder in the fintech space. We're in the process of raising a preseed round and my cofounder hit me with a bomb today. He just dropped out of our startup and wants absolutely nothing to do with it (he won't even help build a prototype in exchange for compensation). We haven't gotten into any conflicts before, he simply said that he lost passion for the project. Now I was supposed to apply to YCombinator but we have 0 technical talent now, so what should I do from here? Because this was out the blue and makes things much more difficult.