In certain situations, especially ones related to trauma or an altering event, it may be possible to remember it faintly. But there are many factors that may have helped you remember this.

Have you spoke about it at great lengths when older? Is it often brought up about how they took the cast off? If so, you’re looking at the idea of explicit (declarative) memory—the storing of facts and events. If over the years you are constantly reminded of this event, it is more than likely that you’re trying to generate a (possible semi-accurate) image or memory of that particular event.

As far as your second comment goes, mother tongue and languages are different all together. When you learn as a yongue age, your cerebral cortex is still developing and your mind is absorbing everything like a sponge. As you learn these words, continue to use them, that language and those procedures are going to get stored in your long-term memory and then you’ll be able to recite all of these words and form sentences without thinking twice—something we would call implicit memory which helps us with procedure memories (riding a bike, writing, etc.).