This is a red-bordered emerald moth. These are common moths in my own backyard. At rest, they're strikingly-green wings are held flat and spread to their sides, and if they're resting on the leaf ...
Browntail moth caterpillars (Euproctis chrysorrhoea) have tiny barbed hairs containing toxins. These poisonous hairs cause skin rashes when touched and may cause breathing problems if inhaled.
If inside is clean, leek moth was not there. Check inside folds of flat leaves such as garlic. Exception: they do damage the outer layer of garlic scapes. Onion thrips are tiny and create shorter, ...