Help troubleshooting broken bike

Back in the fall I was riding home and got caught in a freak rainstorm. I was about 2 miles into a 4 mile trip when my bike shuddered, died, and refused to turn back on. I had to do the walk of shame the rest of the way. I attempted to diagnose the problem at the time but could not figure out what was wrong. Since it's beginning to get warmer again I figure it's about to time to fix it. When I turn the battery on, the indicator lights on the throttle light up for a fraction of a second and then turn off. This only happens once and then won't do it again unless it's been several hours. I've checked all the connections for corrosion and contact and nothing is out of place. I also tried replacing the fuse in the battery. Any thoughts on what part is at fault and what tools I'll need to test it would be greatly appreciated!

open the controller case and see if the water is still inside and if you can, then power up the controller and see if the hall sensors will toggle voltage when you rotate the wheel.