When running in self mode, it is possible that the phone keyboard enters a race condition, this happens if the phone keyboard and Android Auto keyboard are both active and trying to be shown on the screen.
To Fix this, you will need to connect your phone to another device running HUR, or to a car which can Android Auto, then open the keyboard inside Android Auto, where you will see an icon allowing you to toggle the phone keyboard. Turn this keyboard off, and disconnect from Android Auto.
Now when you open HUR in Self-Mode the setting will be remembered from above operation and you will be able to use the search option properly.