From Longman Dictionary of Contemporary Englishunobservedun‧ob‧served /ˌʌnəbˈzɜːvd $ -ɜːrvd/ adjective, adverbNOTICE#not noticedFrank slipped out of the meeting unobserved.
Examples from the Corpus
unobserved• Mr. Fong was able to enter the building unobserved.
