Well, over here at 1:20 000 000 Lithuania has small Klaipeda, but Latvia has no Daugavpils. http://goo.gl/f2ABiy . It has another explanation when relates to 1:20M (ports depicted for small republics). But in my school atlas of the 9th form my home city was absent too on a larger scale map. Also example - Lithiania has Klaipeda, Latvia has Liepaja, Russia has Velikiye Luki (rather small one), Belarus has Vitebsk, but no Daugavpils in Latvia too - http://goo.gl/VoGtvl.