I dragged a villager onto the research table, and she vanished. I just started the game, she just weaned her baby, so I took her back to research when...poof. The game still shows 7 villagers, but she's nowhere to be found, and only 6 show on the details list.

You can read some of the other threads that deal with vanishing villagers.... Arthur is fixing the problem and will release an update ASAP!