By ‘we’d be able to spot them’ Daud suspects Strange really means ‘you’ll be able to spot them,’ seeing as the elf getting caught up in whatever’s of interest to him is akin to slapping blinders on a horse. He could point out that eavesdropping is hardly limited to physical means and could go back and forth on this for a while ... but it all ends the same way, which is that Daud and Strange companionably sharing a drink isn’t like to happen anytime soon except for by happy accident. Strange is a tiring man and Daud is a tired one on the best of days; like as not, if Billie insists about getting him involved in her business, their paths will inevitably cross again.

So he simply makes a considering ‘hmm’ sound that isn’t assent or otherwise, looking towards the pen of goats peacefully working on chewing their cud, placid and unconcerned with the state of the world’s affairs.