You can download an overview of unmatched, and therefore, non-exported transactions using the spend analytics. 

In Analyze > Spend analytics, select Transactions in the Choose type dropdown list and select your company in Company.

You can configure various specifying parameters for your data selection and layout, the date range, and the filter criteria. 

To download unmatched transactions, select the Not matched status in the Status filter only within the Application of filter criteria subsection.

Define your report structure along your informational parameters. For a report structure, our suggested setup is to aggregate information in Rows. The information that may be especially of interest for you to include is the Transaction ID, Original amount, Original currency and Status.

Select Generate report once you’re finished. This generates an overview in the Results subsection, as well as a .xlsx file with your analytics report.