I failed to thaw my fish and I'm ready to poach. Will this still cook properly?

It actually worked out great. Thanks

I think it depends on the thickness of the fish. Thinner cuts should be fine but thicker cuts might be overcooked. How did it go?

Don't see why not - just give it some more time in the poaching liquid. Test by slicing into the thickest part and giving it a visual check for done-ness.