This looks (and sounds, from your description of defoliation) like Euonymus Leaf Notcher, a non-native pest we are encountering with greater frequency as it spreads in the mid-Atlantic. Here is more information on its life cycle and control options: https://extension.umd.edu/resource/euonymus-leaf-notcher

Here are a few additional images for comparison: https://www.marylandbiodiversity.com/view/6587

If the defoliated shrub was Euonymus or something else equally vigorous, it will likely recover just fine on its own with no intervention.

Miri