Then I’d not worry about it. If it’s still got oil in it after this long, then the lubemonkeys managed to do it right.
But I still wouldn’t risk taking it back to them next time.
Actually an oil change is one of the few things I let the dealership do. Around here anyway they’re the same price (and sometimes cheaper) as the quickielube places, AND you get free coffee and cinnamon rolls while you wait in the lounge watching Top Gear on the HDTV. And they wash the car for you.