Two years ago the first ever probe to land on a comet bounced and ended up in a hole with limited sunlight to keep it going. Some signals were received from it with enough data to keep scientists busy, but they couldn't be sure exactly where it was. The comet gravity is so weak that is could have bounced a huge distance.
Today it has been found, just days before the mission was due to end.
Image from ESA
This whole mission is pretty amazing. The scientists need to be so patient whilst their probes take years to reach their destination. There's little chance to fix anything that goes wrong along the way.
Coincidentally I am reading Seveneves by Neal Stephenson that involves travel to a comet.