Testsuite and Testcases are currently loosely coupled ( logical connected ), So in Testcase you will not find any testsuite name where its included. And,  Testcases inside a Testsuite is also stored in BLOB data, not on an exposed column, so reporting on that is not possible currently.

Using an activity you can get the required list. Steps would be to get all the list of testcases ( D_pxGetTestCaseData loads all the testcases for the current app quality settings context), then copy the list it onto a temp page. Then open the suites and remove the matched ones. At the end the list of testcases in the tempPage would not be associated to any testsuite.