Thank you for your post.
When clicking the Find button and no records found, FileMaker will alert you and provide options. However, when Error capture is turned on, FileMaker will display a found set of zero records, so any previous find has been replaced by the new found set. Therefore, you may want to store the last found set before issuing the new Find. That way, if no records occur in the new Find, you can revert to your previous found set.
Let me know if you need additional clarification.