If you truly don't care what the person submitted, then you can log a synthetic Munchkin click (using the Munchkin API).
But I think you're forgetting that Marketo won't know who the person is unless you also include their email address. So, as you suggest, you should perform a hidden form post using the Forms API, including at the very least the Email field. If you search the Community there are several examples.
Also please move the post to Products. "Community" refers to the Nation website. Peer-to-peer support is in Products.