There is absolutely no reason to think that the Romans systematically destroyed Carthaginian writings. No author mentions such an idea, and Punic literature was known to have survived well into antiquity. Punic literature probably simply stopped being copied, like the vast majority of all literature from antiquity--scribes had their priorities, after all, and if nobody was going to read this stuff then what was the point in preserving it. This is especially a problem in the Middle Ages, but it's true already in antiquity--Catullus, for example, was nearly lost entirely by late antiquity, due to a great loss in the popularity of his works under the Antonines. This comment has quite a lot to say about Carthaginian and Phoenician writings, which are often epigraphical. We know of at least one text that was consciously saved, Mago's agricultural treatise, which was translated into Latin. Most importantly, though, the Romans themselves contradict the idea that there was some systematic destruction of Punic texts. Pliny specifically says that the Carthaginian libraries were distributed to the African kings. If Sallust's comment in the Bellum Jugurthinum (uti ex libris Punicis, qui regis Hiempsalis dicebantur) means that the Punic books belonged to Hiempsal rather than being written by them (as I think they must, ex libris is a known formula meaning "from the library of ___" with the name of the possessor of the library in the genitive) then these would be the Numidians