ok. post ist old enough for a proper answer.

We have a similar config, our LogPath is empty, and we can see our logs by just printing them:
docker logs container_name
and, wait for it, in the folder:
ls -lh /var/lib/docker/containers/*/local-logs/

/var/lib/docker/containers/34bdb0801f0dac25fd1874c2c5de5c03f55fa88eb5b4e267442805ff29cd590a/local-logs/:

total 142M

-rw-r-----. 1 root root 90M Oct 6 10:32 container.log

-rw-r-----. 1 root root 13M Oct 5 18:16 container.log.1.gz

-rw-r-----. 1 root root 7.3M Oct 5 08:17 container.log.2.gz

-rw-r-----. 1 root root 12M Oct 5 05:03 container.log.3.gz

-rw-r-----. 1 root root 7.6M Oct 4 20:56 container.log.4.gz

-rw-r-----. 1 root root 6.8M Oct 4 19:41 container.log.5.gz

-rw-r-----. 1 root root 6.8M Oct 4 19:34 container.log.6.gz