Conflict with Jetpack's Photon: Featured Image removed when editing listing from frontend

Steps to reproduce:
1. Install Jetpack, activate [Photon](http://jetpack.me/support/photon), install WPJM.
2. Create a few listings from wp-admin, including both a Featured Image and some gallery images.
3. Create a `listings` child page, and add `[job_dashboard]` to that page.
4. Access that page, and click on edit to modify one of the listings from the frontend. The listing description as well as the featured image and the gallery images are all displayed there.
5. Add a few words to the description, and save your changes.
6. The Featured Image still appears as the "cover image" on the listing's page.
7. Open the listing in wp-admin.
- The Featured Image is gone.

This only happens when the Photon module is active.

Could it be because the image displayed on the frontend is different from the actual featured image (it is served from a WordPress.com subdomain, `i{0-2}.wp.com`), so when the form is submitted when saving your changes in the frontend editor, the media URL doesn't match a possible attachment on the site?

Reported in 2435021-t