Horne also noted Cheeks is "doing well" and the team has been in contact with him since the unknown medical episode took place.
The 60-year-old has been on the Thunder sidelines the last two seasons, as well as four years from 2009-13.
In between then, Cheeks was the head coach for the Detroit Pistons before being fired after 50 games. In nine total seasons as a head coach for the Pistons, Portland Trail Blazers and Philadelphia 76ers, he has a 305-315 career record.
He was also a four-time All-Star as a player for the 76ers.
Cheeks underwent hip surgery in February 2016 and he missed a portion of the season while recovering.