5 week old "pullet" crowed this morning 😳

I was dozing in my recliner this morning, when hearing a noise from the brooder, my husband and son simultaneously exclaimed "what the heck was that?" Thirty seconds later I, too, heard the noise. I knew immediately what the heck it was. My five week old TSC cream legbar "pullet", purchased at a day or so old, (they are auto-sexing, correct?) crowed. It was definitely a crow and it continued to crow three or four more times. I have four roosters, (three silkie, one silkie/buff orpington) and the clarity of this crow put them all to shame. I've never had this breed before so was it possible or likely that a cockrell chick got mixed in with the pullets and I unawares chose it? They only had pullets of this breed. Is it possible or likely that she has heard the adult roosters crowing and mimicked them? Either way, 5 weeks old! I did notice the large comb and wattles but not being familiar with legbars, and trusting the "pullets" label, I didn't give it much thought. Well, shame on me for not doing my research before buying.