While the suction of the motor should hold this section in place when on, it does need something to pull it in line. I improvised with a couple of cable ties until I can see if there is a replacement part.
Update . I ordered and replaced the catch, its called a:
Dyson DC14 Motor Inlet Cover Catch 909235
It took a couple of goes as it appears that the shape of this catch has changed within the DC14 production run. There is a 909235-1 and a 909235-2 .
Mine had a longer earlier style catch with a ribbed section, and was initially shipped the later part variant which was too short. I phoned Dyson, explained and they shipped me the correct part which is still used on another model. Dyson support were very helpful, but full exploded diagrams of their models on their website, would help avoid this confusion.
Fitting it was a bit hard. I needed a long Torx driver i.e not a replaceable bit type, and I removed the two screws located near the catch. I was able to loosen and prize the old broken catch out and fit the new one without a complete strip down
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