Johnny Jump-ups are violas, and I would imagine in some places they are perennials. Some violas are sold as "polar pansy" varieties and often come back after the winter. In your case, it sounds like you were lucky enough to get a seed or two to germinate. Violas, like violets, spead very easily by seed. They're very fun plants. Hopefully you will like them too in the event they start spreading into your lawn!

Cheers,
Dave

Johnny jump-ups are flowers that make me happy! They have a happy name... I love to find them in the spring. I'm in zone 7, and they do reseed here. I hope yours will for you, too.