Martin (1992: 106):
Note that when participating in the prosodic realisation of negation (see Matthiessen 1988: 160-1) anyone, anybody, anything, any + noun and nothing do not realise participants. Thus the contrast between [3:22] and [3:23]: anyone provides a referent for them in the interrogative example, but not in the negative.
[3:22] Did you find anyone?— Yes, they're waiting outside.
[3:23] I didn't find anyone.— *Bring them in.
This claim is manifestly untrue, as demonstrated by obvious counter-examples like the following:
You didn't find anyone?
— No, maybe they already left.