The Form entries are indeed stored into the wp_posts table, and you can access them in the Feedbacks menu in your dashboard.
They should also get emailed to you though. Could you check the email address you specified under Settings > General, and under the Email notifications tab in the form builder?
http://jetpack.me/support/contact-form/#jp-carousel-723
If that email address is correct, could you check that you receive emails when somebody comments on your site, or registers? Since Jetpack uses WordPress' default mailing functions, the emails may not be sent of that function fails on your site.
Thanks.