TiVo let me down...

So last night, i am confident that TiVo is taking care of me and I am going about my business. Only to find out 30 minutes too late that somehow TiVo decided to record South Park instead of Grey's Anatomy. I don't know how it got moved up on the Season Pass Manager list. It's disappointing when you rely on TiVo only to have it let you down. I know these instances are few and far between, but still equally as disappointing.