I was thinking of the systematic suppression of gnostic texts, which was very effective. It would perhaps fit your 'heretical' remark, since the gnostics lost.
There was no real 'systematic' repression of texts in the ancient world, only local and ad hoc. Central powers had too little control of whatever 'system' existed to be able to coordinate and manage anything like that.
During the Diocletian Persecution the (Pagan) Romans destroyed Christian, Manichaean and other 'subversive' religious texts and burned people who refused to sacrifice to the Roman gods.
This was under an official edict from the Emperor, one who significantly increased the imperial bureaucracy, but it was hardly applied empire wide with any standardised degree of rigour. A few hundred martyrs were created, some properties confiscated and some texts burned, but it had minimal impact on the availability of Christian texts.
Communication was too slow, power too decentralised, enforcement mechanisms too weak and cultural differences so great that an edict was more of a 'the Emperor likes this' advisory than a modern, standardised law enforced by the police and courts. Many edicts were completely ignored in many parts of the Empire.
The Pope had even less ability to enforce anything much, and the idea that there was a unified 'Church' in anything other than theory is a mistake.
People look at edicts or decrees and think that they had far more influence than they actually did. Also hagiographies tended to overstate persecutory zeal as a common trope.
Gnostic texts disappeared for the same reason most Christian, Pagan or any other texts have disappeared: no one was interested in spending the vast amounts of effort and money necessary to copy them endlessly for 2000 years.