While Nico was disappointed with the rate of progress that they were making on the cloaking device, they were still making progress, and in a uniquely human fashion, not using any methodology that was known before.
Simple optical camouflage was a simple matter, they could already do that to some extent with Keper technology, but it only blocked eyes and cameras using visible light, so it wasn't in widespread use.
To be considered fully cloaked, a standard sensor suite shouldn't be able to detect the object, and that included sound, thermal emissions, and energy signatures, which any ship they passed or alerted patrol would be looking for.