Collocations for unnoticed - adj.

be, go, lie, pass
The ticket lay unnoticed in my desk drawer for a week.
His remark passed unnoticed.

remain
enter, escape, slip, slip away
She slipped away unnoticed from the party.

completely, entirely, totally
There's a good chance my absence will go completely unnoticed.

almost, practically, virtually
largely, mostly, relatively
hitherto, previously
a hitherto unnoticed detail