Every once in a while this will happen to me. I find the search box will come back if I navigate away from that day, or go the the Activities tab, or some such. Sometimes I have to restart the app. But the search box always comes back eventually.
Starting weight: 192.0 lbs (6/19/2011)
Lowest weight: 154.6 (6/25/2012)
Current weight: 162.8 lbs (1/28/2013)
Total lost: 29.2 lbs
Goal: 132 lbs