One problem related to transmission slip out of gear has been reported for the 2002 Lexus ES300. The most recently reported issues are listed below.
Rough shifting/slipping in lower gears (1,2). When accelerating in stop and go traffic car seems to stall before it suddenly bumps into gear. Intermittently - when accelerated suddenly (moving steady at about 10 miles per hour) transsmision slipped out of gear, engine rpm reached about 4000 rpm. It engaged in gear after I released accelerator.