A drive shaft failure would quite likely result in some mechanical noise, possibly some sparks from metal to metal contact (depending on the exact nature of the failure) all the way to the ground, as long as the main rotors were rotating, because the two are directly geared together.
According to the published pics the driveshaftcover is undamaged down to the ringspant between tailboom and fenestronhousing....
In the early days of the EC135 an ECD h/c had a driveshaftfailure in flight, which resulted in a total loss of the cover and driveshaft, but an successful landing afterwards.
Another EC135 crash was possibly discussed here in the forum some time ago. A japanese 135 lost tailrotor control due to a broken push-pull tube while on maintenance test flight. They cashed and I think, the crew of 2 perished... A vid showed them tumbling out of the sky.