In this paper, we study and analyze data fragment placement techniques to exploit their problems and design an energy-aware fragment placement method in Unattended Wireless Sensor Networks (UWSN). In UWSN, the survivability of data is of utmost importance because sensed data cannot be immediately transmitted and must reside in the storage of sensor nodes for extended periods of time. The data, which have delay-tolerant characteristics, can be exploited by attackers that access the storage to erase or steal the data. Even though data fragmentation methods have been designed to solve this problem, these works do not consider a critical issue of where to place data fragments in the sensor network. In this work, we show that basic existing methods of data fragment placement have some problems, especially in terms of energy efficiency and data survival probability. Based on our analysis, we propose a lightweight method that allows us to efficiently select sensor nodes that are used to safely distribute and place data fragments. We show through simulation and preliminary testbed analysis that our proposed method can improve the overall performance of data fragmentation.