Method 1 (v5.5 Beta only) Since " COBIT_DS3" is a pen Reports (it's better if you can dock Reports on the left or right side of the Plex rather than at the top or bottom, so as to give you a nice long list), set Sort to Name, then look down the list to the first Thought starting with prefix, o COBIT_DS3. Click this Thought, then scroll down Reports till you find the last thought starting with COBIT_DS3. Shift+Click this one in order to make a contiguous selection (including all the ones in between). Then go to the Edit Menu and choose "Add Report Results to Selection." Then, either from the Edit menu or the Selection Box's R-context menu, select Forget Selection. Method 2 (v5.0 and 5.5 Beta) Locate them using Advanced Search on Names, putting COBIT_DS3* in the search string, then choosing Edit > Add Search Results to Selection.
Hope this solves your problem. Remember, once you update your Brain to 5.5, you can't revert it to 5.0.
PB 126.96.36.199 on Windows XP, J-1.6.0_17