Acacia logs disappeared

I booted up my world that I normally play. This, ironically, is the demo world, which I have a liking for and that I've built up greatly. However, crossing my massive footbridge I noticed that my vertical acacia logs had disappeared! Note that this seems to apply only to player-placed logs, as naturally generated (grown) logs don't seem to be affected. This also occurs w/o a block update, torches are left floating as shown in the pic.

Now I have to redo my whole bridge again! :-E