I've never had a problem pitching into a recently sanitized carboy. My carboys usually have a bunch of sanitizer bubbles left in them before I add the wort. Did you aerate the wort before pitching? Usually shaking your carboy vigorously for 5 mins will do the trick. What was the "use by" date on the yeast? Lastly, WLP001 ferments best at 68 - 73 degrees, so try to keep it in that range during fermentation.