The Black Eyed Peas frontman, who mentored the likes of Tyler James and Jaz Ellington in the BBC contest, likened the experience to "a lovely dream".
"I felt very strange not doing #thevoiceuk this weekend," he confessed on Twitter.
"I felt as if it was all a lovely dream and it never really happened...#imisslondon."
will.i.am said earlier this month that he "definitely" wants to return to The Voice along with fellow coaches Jessie J, Sir Tom Jones and Danny O'Donoghue.
The Voice UK was this week declared the BBC's biggest entertainment show in a decade after its first series achieved a consolidated series average of 9.2m viewers, more than the debuts of Strictly, The X Factor and I'm A Celebrity.
This was in spite of the show losing more than half its viewers during the Live Stages and will.i.am himself admitting that it "doesn't make great TV".