The recommended direction for Lost is downhill.
While Lost is not the gnarliest trail in the valley, be prepared for loose chunky rocks, small drops, and a few steep descents. In all, it's a fun and challenging way down from Little Rainbow
Maintenance on Lost is ongoing to help keep the trail sustainable. Summer rains erode the trail, so watch for rutted out sections. Work has been done to add berms to some corners but not yet all that need them.