Where there's one cutworm, there are more. Sorry.
The best defense against them is to understand how they work. Cutworms must totally wrap themselves around the stalk of the seedling, literally touching head to toe (so to speak) so that they can chew. If they can't fully wrap around the plant, they can't chew. So, soon as you plant things, immediately slip a length of thickish twig up against the plant stalk and into the ground so that the stick protrudes above ground a bit. There must not be space between twig and stalk for the cutworm to squeeze through. Now the cutworm cannot wrap itself around both the twig and stalk to do its damage. Since I started doing this method, I've never lost a single plant to them.
Some people will cut a short length of plastic straw, slit the straw lengthwise and slip it around the stalk and a bit into the ground. It works but its a real fiddle, especially when you can't find straws to buy. Twigs are plentiful and free.