That's quite poor form from the agency.
I think the right thing to do is to tell your current employer that their recruitment agency is now actively working to take their staff away. I'd expect your company to fire the recruitment agency.
There's a (significant) chance the new role has been seriously misrepresented. Perhaps contact whoever the recruiter is now working for directly?
This is standard agency practice.
Place candidate. (Hence you know they are employable)
Pass rebate period (Whatever time period the agency has agreed with the employer after which the full fee stands)
Attempt to move candidate elsewhere for a fresh fee.
It's good business sense really. The moral question is a different matter though