I can assure you that Buffett is not kicking himself for entering $ULTA last quarter and that they have had a disappointing quarter, he was likely aware of this and is happy about its long term plan and trajectory and will probably be taking advantage of this pull back today.
Price hit a low of $342 today and has already recovered to $360 already
The 0.618 fib is at $296, where the price was going to until Buffett revealed his position.
This is the standard pull back level, this would also be an attractive level to add if the price flushes down to here.