Thanks so much everybody -- I took Shane back today to the farm, and the owner agreed that she's a he. Rooster tail feathers developing, and generally just a bigger bird than her "sister" who'll be staying. Still seems strange that he never crowed, but perhaps he was just waiting for the opportune time to surprise me.
At any rate, I'm now the proud owner of two beautiful Golden Comets (sex link, definitely hens) which are 6 weeks old. I've made a separate area in the chicken run with a temporary "coop" while they grow and will merge all the chickens together probably when these are about 3 months old, maybe 4 depending on how they develop.
Thanks again to all!