Lisa Winter, IFLS:

While Philae initially landed on the target landing site, the harpoons meant to secure it to the surface failed, and it bounced twice before coming to rest (albeit tilted slightly) on the shady edge of a cliff.

This location was problematic, as it meant that Philae would not receive enough sunlight to recharge its solar panels. After about 60 hours of transmitting data about Comet 67P/Churyumov-Gerasimenko, Philae’s battery ran out and the probe went to sleep. There had initially been some optimism that the probe might wake back up as the 67P/C-G gets closer to the sun next summer, but there’s just one problem: nobody knows where the heck it is.

Man, that sucks. I sympathize with the guys at the European Space Agency; I lose my keys all the time and it is not fun.