Welllllllll... back to this debate... DNA testing takes time, so we don't really know yet what they found. If the perp was smart enough to clean up the scene, one would imagine he was smart enough to clean up a transportation vehicle... however, if you strip the vehicle apart, DNA could have been washed into any number of nooks and crannies...
... and you don't necessarily need to confiscate the hose, just like they didn't pull up the sidewalk for court to prove there was blood evidence. That would make for a very long trial if every item had to be presented, rather than just a picture or a theory.