Could be the input shaft bearing on the gearbox. When the DMF came apart it could have put undue forces on the bearing and damaged it. Bearings quickly self destruct in short periods of time so be careful if it is the cause. If it is a similar design to the mk1 5 speed box then the bearing is possible to change without box disassembly, but it does mean the box coming out. Can't be the release bearing or other clutch components as the noise would be constant with engine noise.