As I understand it, the armour in question was chain-mail (lorica hamata). mail was adopted by the Romans after more conflicts with the Gauls, such as the battle of Telamon.

Telamon happened in 225BC, after the first Punic War but before the second.
So the Punic commanders did not encounter mail-clad legionaries until at least 217BC when Hannibal killed a lot of them. However, since the Romans got the idea of mail from their Gallic neighbours, and those Cisalpine Gauls were Hannibals allies, Hannibal must have seen the stuff on the backs of Gauls before he saw it on Romans.

Perhaps the Roman style mail differed from the Gauls? Or more likely after Lake Tresimene there was suddenly a lot of Roman chainmail available to Hannibal.