They were concerned with who bought my train ticket once they saw the receipt on my phone. The NYPD officers didn't seem to believe me that some organizations work for justice and organize these legal protests. Each time they touched my phone, I told them I didn't consent to having my phone searched. (They held my phone during the interview, and I can only hope they didn't poke around it — although they wouldn't have found much to interest them, unless they like Bernie GIFs.)