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