First off, each state has their own laws and many lakes have their own regulations. As an angler you have the responsiblity of knowing the laws and regulations of all of the bodies of water that you fish.
Secondly, you were fishing with a lure designed to catch a wide variety of fish. You many have been hoping to catch only bass, but the lure is meant for a variety. So, you were, in effect, fishing for anything that would bite (trout being a possibility). Therefore, if there are trout in that body of water and you need a trout stamp to legally fish for trout then you should have a trout stamp.