The fact that it got wet without being driven helps a little, but not much. You need to check every possible entry point within about five feet of the door. That includes windows, awning mounts, roof rails, lights, etc. Also, check any window weep holes in the area.
A tremendous amount of water can be dumped off your roof above the door. On my previous coach, I added a channel above the door to help divert water. I never found my door leak, but the channel stopped it.
2019 Phaeton 37BH