There almost certainly were Carthaginian accounts of their own history that were destroyed. And it might seem easy to blame their destruction on active malice by the Romans, and to some extent that's not wrong, but preserving ancient texts has always been an ongoing process that relies heavily on active work by scholars who would make copies over the centuries. We've lost things that ancient people very much wished to preserve, such as poetry by the nine lyric poets. Some of the only stuff we have from Sappho, for example, comes from fragments of worm-eaten papyrus dug out of ancient garbage pits in Egypt.

One of my ancient history professors described the ancient world as an enormous mansion with thousands of rooms. We are able to peek in through the keyholes of a few of the doors, which gives us a very clear view of very small parts of those rooms, and a slightly hazier view of a little more. Then there are rooms with no keyholes that we can't see in at all. We know there's something there to see, but we have no way to peek in. Carthage isn't the only ancient civilization we know far too little about, it's just one of the more famous ones.