Some other reasons why you may not be seeing your product(s) in the usual galleries are:

1. The customer simply doesn't display their artwork  on the web.
2. The artwork is being displayed at "obscure" sites/galleries you don't know about.
3. Your products are being used for projects outside the Poser community.
4. The customer just hasn't gotten around to using your product(s) yet.

I'm guilty of the last one.  In the last few days I've been going through my purchases and downloads, organizing stuff and thinking about what I want to install for when Carrara 6 is released, and was shocked to see just how many commercial products I had completely forgotten about, haven't used or even installed yet!  And some of it is from a LONG time ago...I'm talking a year or more.  And I won't even get into the freebies!  I have so much stuff, I'll never be able to use it all...and yet I keep getting more!

But when I post a new image, I almost always (about 99% of the time) give credit for everything I use, both free and commercial. 

"You don't know what we can see
Why don't you tell your dreams to me
Fantasy will set you free." - Steppenwolf