As all have said, very glad to hear you're OK!
I wonder if the physics of a (any) 3-wheeler cause it to naturally become more unstable in hydroplane conditions? A 4-wheeler has one more contact patch, so as long as 2 wheels are making contact, it will continue to go straight, relatively speaking. Even in a car however, hitting deep water will throw the vehicle around a bit. In a very light car with only 3 contact patches, I could imagine that the dynamics get dicey very quickly in deep water.
Would be interesting to see if other three-wheeler communities have experienced similar things. I would think the Slingshot would behave the same, perhaps even worse with its wider tires.