I understand that you are not able to get some of the buttons you usually get on your TiVo when running the SlingPlayer for iPad.
First, I recommend you to verify if your TiVo model is included on the supported devices list. The following link will allow you to get this information:
If it is not, that means that some of the feature might not be available. Finally, keep in mind that the SlingPlayer for iPad does not offer the virtual remote control skin feature as other supported Mobile devices.
Hope this helps.