All of my Lean Body Mass data is gone!

I've been entering, by hand, my Lean Body Mass data every day since I got my iPhone 6 back in October.

Today, as usual, I entered a new value, but looking at the graphs, it's the only entry. All of my months of data is simply gone. I've killed and restarted the Health app, and restarted by phone (both normal swipe restart and by holding down home/power). No dice, all my data is still gone. No, I did not clear it -- I don't even know how to do so, and the phone's been locked and in my possession the entire time since yesterday, when I definitely did have all my data.

Is there any way to get it back?

Randomly losing months worth of data is totally ridiculous. I've been hoping this app would be improved over time (like, say, the ability to look at another day's data or -- gasp -- be able to scroll the graphs), but if it's going to just lose data it's worse than useless.