Where can I find Donald and Douglas?

Surely they did release Stepney, Skarloey, Rusty and (possibly) Duck, but Oliver and Lady would be impossible since Fisher Price never made them. That factory merely has access to FP's old equipment from before 2014, and none of the Asians who work there would know Thomas & Friends well enough to know the never made engines (or wouldn't be able/allowed to add new designs and moulds anyway).