I am still not sure if I used the correct line at ATH. In the course of IAD-AMS-VIE-ATH, UA/OS had misplaced my checked bag, and I just stormed out of the baggage claim area without choosing a door too carefully... to find myself in the entrance hall with my large carryon, no customs check, no immigration check. I'd arrived from a Schengen country of course, but I'd been waved through at AMS too, and I assuredly do not pass for a native in, well, any European country. Was a little concerned that if there were trouble there'd be no entry stamp in my passport.

No such shortcuts on the return to IAD of course.