‘ And so it was that at the end of three days, after they had made a treaty-covenant with them, that they heard that they were their neighbours and that they dwelt among them.'
Then after a few days had passed (the regular ‘three days') the Israelites learned that the Gibeonites in fact ‘lived in the neighbourhood' and ‘were dwellers in the land'. Note the parallel descriptions of their status which would ensure the point got over to the hearers. It was not the kind of secret that could be kept for long. Soon everyone would know about it. People would be gloating and laughing at the way that the Israelites had been duped. It was too good a story not to pass on.