This should work exactly the same in FileMaker 12 as in earlier versions. I suggest taking a closer look at the details of how you set this up. On possible explanation is that you have two table occurrences that refer to the same table. If you find the records on a layout that refers to TableOccurrence1 but import records from TableOccurrence2, the found set in TableOccurrence1 has no effect on what records are imported from tableoccurrence2.
You are correct - many thanks! I should have thought of that. The table itself has several aliases and hadn't mapped the exact one that I had performed the original find.