amrika basera nepali nagarikata pauna ta garai chha hai. embassyle nagarikata didaina jasto lagchha malai. you have to go to your VDC or DDC office and apply for a new one. since you are here, ask your parents to apply on your behalf. but you'll have to write a letter (love letter hoina, nibedan) addressing the VDC or DDC head stating that your nagarikata has been lost and you need a new one i.e. pratilipi. also state that you are abroad and your circumstances don't allow you to travel to go to nepal. sign it, mail it to your parents so that they can take that nibedan to the DDC or VDC head and start the process. you might be required to send your pp sized pics, copy of passport and/or birth certificate.
yo naya pratilipi payepachhi chahi ki aamako dhukutima jatan garera rakhnu, ki aafno ghatima badhera hidnu, nagarikata bus pass jasto hoina k, harayo bhane banauna ali jhanjhat nai hunchha

 jhyamma: DDCs make 2 copies of nagarikata when you apply for the first time. one is given to you and the other remains in their locker as a back-up for situations like this. so, metalgal might be able to get that without having to go there.
and yes, you're right, US ma nepalko nagarikata kahi pani use hudaina. i didn't even bring mine with me, not even a photocopy. so, metalgal, you can just chill, and get a new one whenever you go back to nepal.