Sleuthing in wikipedia and elsewhere suggests that this is where the salivary gland that was originally infected (the one under the jaw that was mysteriously swollen during the prodrome of what turned out to mumps) drains. It drains _uphill_. Wow. Who knew? So all that's left is some painful inflammation at the end of the submandibular duct. One hopes that it will shortly do what the parotid did, drain and shrink back down to its normal, healthy, un-inflamed state.
There's still a chance that this was a stone. But the descriptions of the kind of pain, and sensitivity to when you eat and so forth just did not sound right to me. Also, the time frame is a good match for mumps, and Teddy was acting like he had cheek pain and was looking unusually chipmunky while sick. And I'd had my immunity checked and did not have it. And there was that dayish of stiff neck/fierce headache. So I'm still thinking mumps.
Dr. Google is pretty cool.