Board Thread:False Info and Speculative Discussion/@comment-4723271-20170918140954/@comment-26819589-20170921185338

^ Deuc wouldn't have really needed his heightened hearing(so his was most likely turned off). Scott & Malia(before she sits back & let The alphas fight) were flip flopping between senses & we're focusing their hearing on something more specific(trying to find Deucalion & not crash into anything).

Scott practically tuned out a whole hospital just so he could focus on what was going on in his mom surgery. Peter was with Lydia for most of the episode. so his was most likely turned off.

Short & simple answer, they just were focused on to many other things to take notice of the hunters. 😎