You aware that Samehada is a sensor, right? It tracked down Bee from only Kishi knows how far away, and directed Kisame right to him. Not to mention fusion mode. Also, if Mizu Bunshins come into play, it'll make it even more difficult for Mu.
It's a pseudo-sensor because it's drawn to chakra in extremely large quantities, like Bee's. It won't be drawn to Mū's chakra, which isn't that big in quantity, relatively speaking.
Don't see how fusion or Mizu bunshins help, since Mū isn't getting caught in the dome, and is also a sensor and can swing jinton across his body similar to how Ōnoki did in the scan I posted.
Edit:
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Here's the scan pertaining to the Samehada being a quasi-sensor. "Scent" here is obviously used in a metaphorical sense, but from here the most we can deduce from Kisame's statement is that the Samehada is attracted to chakra in large quantities. It doesn't mean that the Samehada will have the same inclination towards other chakras.