Yes I'm sure it came from your new plants. In the future I would soak new plants at a 1:3 or 4 ratio of hydrogen peroxide 3% to water. Leave them soak 20 minutes before putting them in your tank. This generally kills most snails, eggs, algae, and other unwanted hitch hikers.
Also if you found 1 snail in your tank there are probably several more.
If you don't want snails then I would remove any you find.
That kinda looks like a ramshorn snail. Hard to tell from that picture though. Is it flat on the sides? If it is, then you have a ramshorn snail. I like mine. They help keep the plants and substrate clean and are cute. If you do not overfeed than they will not get out of control. Feed once or twice a week. You can sell extra as feeder snails or tank cleaners. I just thinned mine out because I over fed in one tank. Lots of people like them to feed their snail eating fish or assassin snails.