I mean if the field in the far region is proportional to the Hankel function, then the thing must radiate and metal nanoparticles do not fluoresce.

I think metal nanoparticles do scatter, coherently with the excitation (at the same frequency), according to the hankel function. Incidently, they also slightly fluoresce, through hot-electron relaxation, incoherently with the excitation (at lower frequency).

Scattering is not a problem, but existence of a mode without external field is. It leaks energy to radiation even if one assumes ideal metal with strictly real negative dielectric function. There is no state.