If you find there is no recognition of SAP controls using SilkTest.

Then this behaviour is most likely occurring because SAP Automation/scripting is not enabled.  As a general hint, you always need to trigger a server roundtrip on SAPGUI to get actions recorded, because we depend on the SAPAutomation and that only delivers us actions when a roundtrip from the GUI to the server happens. 

You can check if the GUI scripting is enabled by checking if "Script Recording and Playback" menu option as shown below is available.(Click on the very right icon below the main menu, one of the last submenu entries) on SAP GUI and try recording and playing back some steps against the SAP application.

If the SAP GUI scripting is not enabled, then you can contact your SAP administrator to enable the same for use. Also, the following entry from the Internet details on how to enable SAP GUI scripting:

How to Enable SAP GUI Scripting in 3 Easy Steps