Can you let us know what the church said. Would be interesting.
Saying they were dressed the same and asked the same questions worries me, My best mate dresses totally normally, nothing different about her or any of her church going friends, and saying they asked the same questions also is no guarantee, a "real" Mormon could have asked them the same questions a few days earlier, and they could be using this to trick you into thinking they were the real deal.
Good excuse to get your bf to stay round more often!