Support for SermonSpeaker 4.x is canceled as it is for Joomla 2.5. I will gladly assist you with minor issues but I will not fix any bugs anymore in this releases.
The fix is to upgrade to SermonSpeaker 5.x and Joomla 3.x, which is better anyway.
So far it's not possible to search for a speaker. But you can create a view with the list of speakers where you can get the sermons of a specific speaker. Or you can click on the name of the speaker in a sermon and get to the speaker view.