I'm sorry, I'm not directly answering your question ("Why didn't they *mention* Data?"). I couldn't find any production notes, and I couldn't reach the story author (Brannon Braga) or the director (David Livingston).

*But* - I do have a decent *in-universe* explanation of why Data's story didn't matter.

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**Data was a unique being that Starfleet discovered, consisting of hardware that had yet to be reproduced.** This ultimately led to him being granted the full legal status of "person".

**The Doctor was pure software, and was entirely designed and programmed by Starfleet.** Even after litigation, he still wasn't granted the status of "person". He was only granted the "economic" status of "Artist", which gave him the right to control his holonovel.

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Pulled from [Memory Alpha (the Star Trek wiki)](http://memory-alpha.wikia.com/wiki/Author,_Author_(episode)#Continuity):

>While it had been determined that Data, although being a machine, was not Starfleet property and thus had the right to choose what to do with his life (and thus could most likely be considered a person), it seems the whole process had to be repeated for The Doctor and fellow holograms. The situation here is even more complex than with Data, since Data was a **unique single being** who was **not created** by Starfleet (he was **found** by Starfleet personnel), while holograms were **programmed and designed by Starfleet** and integrated into ships, space stations and other Starfleet property. In the end, it is not acknowledged in this episode that The Doctor is a person, but he is rather granted the status of an artist.