Congrats your buddleah or butterfly bush likes where you planted it. It is just happy it did not suffer a very cold winter. Don't worry about the foliage that stayed as new growth will soon cover it up. You can also prune back the butterfly bush in early spring and the new shoots will have only fresh new growth without the faded leaves from last summer.  Some varieties are more hardy than others and looks like you have one tough shrub. Enjoy. Keep growing, Marianne Binetti