Open the Uploaded Files report. You can search by file name, transaction ID, and a from and to date range.

Each row shows the transaction ID, the identifier you gave the campaign, the file name, the uploaded and processed counts, the upload time, and a Download link for the original file.

This is why the Identifier field is worth filling in properly when you compose. A list of campaigns named “test” is no help three weeks later when someone asks what was sent.