Although I'm not in the biz of stock photog, I feel for all you ppl who are there. This would really devalue your work. I hope this is a one-off pricing exercise to get Getty's share price on track and thereafter, getty will revert to their normal pricing!
It is my view that it would be an uphill struggle for you. Sure you can sue someone, but whether you can make out a case or try to push a new cause of action (short of defamation or impersonation or similar grounds from past cases) and get judgment is another question altogether
I think everyone can recall that Niki case where she raised such a huge ruckus, posted in her blog that she's going to sue here and sue there and talked to this and that lawyer, and the next thing we know, the blog is closed down and a deafening silence - there was no news of any suit having been filed and she probably just slunk away into the background after her initial big ruckus.
However, if you said it was for a massage ad, it may be similar to the Hanis Hussey case where her photograph was featured in an ad for social escorts. In that case, the grounds of action was based on defamation and copyright infringement (she got an assignment of the rights from the original rights holders) and not on model releases or the lack thereof.