IPA: /ʌnˈnoʊtɪst/
KK: /ʌnˈnoʊtɪst/
Not seen or recognized; something that goes without being observed or acknowledged.
The small details in the painting often go unnoticed by most visitors.
Unnoticed → It is formed from "un-" (meaning not) and "noticed" (from the verb "notice", which comes from Latin "notitia", meaning knowledge or awareness). The word "unnoticed" means not being aware of or not being recognized.
Think of 'not' ('un-') being added to 'awareness' ('noticed') — that's why unnoticed means something that is not recognized or seen.