Cohabited? Is there evidence that they were picking out furniture together? The article suggests that the crippled-up amphibian crawled into the burrow of a hibernating proto-mammal and then they were both killed. Proto-mammal could have been dead for years before the amphibian crawled in, so "cohabited" seems like a big assumption to me.
During emergencies, fires, floods, torrential rains, various species that might normally be hunter and prey will often ignore that kind of relationship while seeking refuge.