MobileRead Forums has an interesting post regarding the search feature.

To perform a search, follow these steps:
1. If the bottom of your screen is not displaying the Search line, press the Search key.
2. Type in your search criteria. You can use whole words or partial words, and no
distinction is made between lower and upper case.

Unfortunately, the poster is not able to get partial search working well. As written, the * is under the sym menu. Do these steps work for you?