It does mention exactly this. "Mr. Miranda was in Berlin to deliver documents related to Mr. Greenwald’s investigation into government surveillance to Ms. Poit

It does mention exactly this. "Mr. Miranda was in Berlin to deliver documents related to Mr. Greenwald’s investigation into government surveillance to Ms. Poitras, Mr. Greenwald said. Ms. Poitras, in turn, gave Mr. Miranda different documents to pass to Mr. Greenwald. Those documents, which were stored on encrypted thumb drives, were confiscated by airport security, Mr. Greenwald said."