I take it that means your 1yr trip was made last year? Did you read the rules concerning breaks in continuous residence, 'cos if not, I really recommend you read them now.
Up to this point you haven't committed visa fraud, but if you don't tell the IO about your trip and overseas employment, you will be in big trouble when they find out. Bear in mind the officer will ask to see your passport during the interview, so he may very well see the entry stamp for the trip you forgot to list.
Several outcomes are possible:-
- during the interview you may be asked to withdraw your application, and resubmit it once you have completed a 4yr+1day continuous residence from the date you returned from your trip.
- USCIS may decide you were deliberately lying by omitting the trip, and subsequently issue a NOID. This could be bad as it might negatively impact future attempts to naturalize.
- you may successfully persuade the IO that your trip was temporary in nature and thus you did not break continuous residence. Frankly I doubt this outcome because you admit you were employed overseas - typically thats a deal breaker unless it was a simple overseas assignment for your (prior) US-based employer.
- you may continue to forget you ever took the trip, and somehow get away with it. Trouble is, you'll never know when that'll come back to haunt you... not recommended.