I logged in and expected the terrain of my town and surroundings to load normally.
At least 2 (most likely 3) chunks of my town were replaced with the newly generated ones. 2 mobs: female familiarized cow and a female familiarized pig disappeared.
Date: the 29th of October 2016
Time: 17:01:13 (the system time of making the first screenshot of the event right after is 2016-10-29_19.01.13 but the difference between the server time and my system's is 2 h.).
Place: around x 6118, z -11209.
Important detales:
There were chiseled blocks in 2 chunks that disappeared.
when logging in I saw "Downloading terrain" twice.

I hope that those broken chunks can be fixed and the animals can be returned.

images of "before" and "after: