UPDATE:
I've filed a claim with title insurance and have been assigned an attorney. All attorney fees are to be covered by my insurance.
My closing attorney has something to lose since she's the one that reviewed the title and called it good, so I'm no longer directly working with her.
Rocket Mortgage is still pursuing the foreclosure.
Title Insurance has admitted to me that they may have to eat this one and pay the balance of the mortgage owed to Rocket Mortgage if fault is not found to lie with my closing attorney who reviewed the title.
Apparently the closing attorney had reason to believe the old debt had been settled, so she sent out a "letter of satisfaction", stating that the debt had been satisfied. Rocket Mortgage then had 30 days to respond. After 30 days with no response, she proceeded to close the transaction. Nearly two years later (now), Rocket Mortgage is filing for foreclosure.
At this point I'm 99.99% sure that life will generally continue as usual for us and our rental property, but I'm not relaxing until the ink is dry and the debt has been settled.
I'm scheduled to speak with my appointed attorney this coming Monday. I'll update the post upon any major developments.
Thanks to everyone for your insightful and actionable responses.