Horne was one of a number of internationals returning after World Cup duty and the scrum-half says it was important to be back in action after the disappointment of Scotland's exit at the group stages.
Speaking in The Scotsman, Horne said: "After you've had a disappointment the best way to get over it is to get back out there and play. It was so nice being back in Glasgow again, seeing all the boys again, all the staff.
"I was delighted to be back and it was easy to get up for my 100th game. There was a chance to go out there and put some of those wrongs right. It was a nice way to get over it. I was just so looking forward to getting out there and getting the win - which we did."
Horne was able to share the occasion with older brother and fellow centurion Pete - now an assistant coach with the Warriors - and other family members who were watching from the stand. "I always say playing with him was the highlight of my career," Horne said of his fellow-Scotland international. "It would have been cool if he had been on the field still. But we have a great relationship and I am thankful to have him as an older brother."