But before the Brawn rescue deal materialised, Button's management was scrambling for a seat.
"Last minute he got a deal but I remember his management were asking us whether even Toro Rosso had a drive," Horner is quoted by the Daily Mail.
Horner made the comments whilst admitting Button, 33, has impressed him "enormously" since becoming champion and then switching to McLaren.
"The team went from Lewis (Hamilton)'s team pretty much exclusively ... maybe the relationship (between McLaren and Hamilton) had run its course.
"What factor Jenson played in that, I have no idea."