The more I thought about it, the more that sounded like a temporary connection issue, weak battery, etc. I figured out how to clear the codes and now it just has the one for the FR sensor.
I checked resistance on the sensor and it is in specs. Took rotor off and - there is no tone ring! Well, that explains that. The rotors have obviously been replaced recently - someone obviously did some work and removed the tone ring and didn't put it back on. Broken I guess, and they didn't wanna buy one.
They have them on eBay for $25, but it shows just a toothed ring - no mounting "horns". Svc manual doesn't show that as a separate piece...not sure what the deal is there. Local dealer has one for $115, I think I'll go look at it and probably just buy the **** thing.