Ross had a long history of accessing internet resources on the internet without going through TOR, such as his email acct. Also he has an email acct !

He had fake IDs shipped to his home address through USPS.

The federal agencies definitely knew who he was already. The scene in the library is noteworthy but they would have Got Him without it.

He was at the library not a coffee shop. I bet they still could have got him at home: Swat kicks he door in, shit! Lock the laptop! Slams the lid. Notorious Linux suspend bug kicks in and it fails to suspend. (You can tell because the fans keep going) Shit. Open, slam, open, slam. Hang on guys, I need to like modprobe or something… Shit those bracelets hurt.