So, very interesting findings tonight after pulling the subwoofers out from under the seats.
Turns out my intuition on this was correct. The speakers are not blown. It is a connection issue. One of the leads that connects to the voice coil is broken off of BOTH speakers. If I connect my multimeter to the end of the lead that is still glued to the cone and the other good lead I get reasonable resistance readings. The cone moves freely as well so that's another sign that the speaker itself is fine.
So it looks like this is just a case of a defective part. In my case it looks like the same thing happened to both woofers over time. That would explain why I noticed no bass when I faded from one side to the other a while back. Then eventually both were disconnected.
The amp is fine and my aftermarket sub in the trunk is providing some extra fill in the mean time. I just turned the crossover off.
So, I'll take the subs to the dealership to show them what happened and hopefully they won't hassle me and just order the parts. I would fix it myself, but the woofers are so low profile that getting a soldering iron in there is risking damaging the cone.
Here's a pic of the lead that has basically disconnected from the glued portion of the wire on the cone. You can see the other lead that is still connected fine in the background.