So were they actually caught with anything incriminating, or is the only thing identifying them the IP address that the FBI seemingly obtained through now class

So were they actually caught with anything incriminating, or is the only thing identifying them the IP address that the FBI seemingly obtained through now classified means? Is the TL;DR: They were caught with child porn, but that evidence is inadmissible because the warrant that let the FBI find it relied upon this "NIT", and the FBI won't reveal the NIT?