Does my car have two catalytic converters?

Yes, your car has two converters under it. There is the front unit which is mounted right to the engine as part of the exhaust manifold and then there is the undercar unit that is located under the middle of the car in between the front flex pipe and the middle muffler.
If you replaced the one under the car then you replaced one that isn't monitored by the cars systems, the front one that is part of the exhaust manifold is the one that is watched and can set codes.
The front one isn't fun to replace but it's not that bad. You start by getting the car in the air, then disconnecting the O2 sensors and removing them. Next you remove the lower and upper heat shields and the manifold brace under the car. Then the shield over the manifold. Now disconnect the flex pipe from the manifold flange and unbolt the manifold from the engine. Now clean up the gasket face and install the new gasket and manifold. Then reverse the rest to put it back together.