Update: Originally this was related to thinking I'd sent money to the wrong person, but it turns out my friend did receive the money. Revised this to be much simpler:
Q: There doesn't seem to be a way to get username / email info from the activity page - how do I view my transactions with a particular user?
A: Next to the "send again" list you can click the vertical ellipsis and select "Manage contacts". Clicking a contact then brings up the list of transactions.
