Have any of you rescuers had this happen?

Three weeks ago at Petsmart someone dropped off a gorgeous spotted tabby kitten, who was about 7 months old. Finding no "equipment" I judged it to be a female, and named her Lily. The vet at the clinic agreed, it was a female and probably unspayed.

Last Tuesday, Lily goes to the vet, and lo and behold, they go to spay her, and no female stuff inside! "She" turned out to be a male, who must have been neutered very young, at 8 weeks. This suggests he came from NYC, where they routinely alter at 8 weeks. Anyway, "Billy" boasts a shaved belly, is recovering, and goes to his fur-ever home tomorrow!