How long have you owned the car and have you ever seen water there before? This storm that went through was not a regular storm and the rain came from all different directions. You might not ever see water in the car again. I heard New York and north they had 8 inches of rain in one day. You might not ever see that again in life. I would just keep an eye on it and if it happens again see if you can find where it came from. You might think I'm crazy but I've been around longer than most here and have seen a lot of strange things happen like this.

Just trying to help.

 

Open the sunroof and the drains should be self evident

 

Yes, definitely check the sunroof drains. Have had this issue before.

 

for the BACK passenger floor you may be getting water coming in from your trunk lid area. it can go thru the tail light and run down the interior wall and onto the passenger floor. check your trunk gasket and your tail light gasket for leakage. also there are some round flat plastic body plugs under the car, if those are missing or not seated water can get in.(check these first)

you can try to emulate the situation by drying up what you have then remove your trunk trim atthe tail lightsthen pour water around your trunk lid drain area and observe where it is going.

gluck