So.... The initial problem of the starter engaging, spinning, but not stopping the spin, has not happened again. I checked the connections, but nothing seemed out of place, and I had forgotten about it.
However, this last week the starter has seemed slow to engage. That is, I turn the key, and there is a normal click, but then an abnormal amount of time between the turn of the key to when anything happens. I can hear the fuel pump, the other solenoids and relays, and I can hear the click at the starter, but nothing for a second or two, then it will fire up as normal.
But it would not start at all after work today. Click, but no spin. So after trying to knock on it with the only thing I had, a multi-tool. I got a few blokes to push me forward a few feet, while I dumped it into 3rd gear to jolt it, without the key engaged or in start. The car then started perfectly normal.