This has been a common problem ever since the beginning of the use of AAM axles in Ram trucks starting with the 2003 model year. If you do a "Search" with the words "axle vent hose" you will find multiple posts as far back as 2003. I remember re-clipping the vent hose to the frame on my '03 3500 shortly after I received it. It hasn't fallen down since.
Bill
Bill