It appears there was some miscommunication as TMZ reported Sting was already at home resting right around the time WWE reported Sting would be in the opener. The WWE announcement was up on WWE.com for no longer than 15 minutes it appeared. Dave Meltzer of Wrestling Observer Radio noted today that the Sting RAW announcement was up around 4pm PST.
Regardless of the misinformation, Sting was not at last night's RAW and was at home resting in Dallas, which is about a 6 hour drive from Laredo. Meltzer adds that Sting was not booked for Hell In a Cell so his WWE status is up in the air right now.