There are numerous drains, but the ones that most often cause problems for the interior are the 2 underneath the clamshell (where the convertible top stows). One on each side in the rubber/foam liner. Then two in front by the battery and one for the AC evaporator. Here's a link to where to find them all...
Mike Focke's Water Drain Link
Hmmm, now having said that and re-reading your post, the drains may be your issue but............ water in the umbrella holder (the tray on the passenger sill), leads me to believe otherwise. You may have unintentionally left the window open... or down a bit. If the door wasn't closed all the way, the window won't go up the 1/4 inch or so it needs to seal w/ the top. With a heavy FL downpour in the right (well wrong really

) direction, water could easily get in.
If the door was closed all the way, then you may have an issue w/ the micro-switch in the door. Does your window drop a bit when you pull the handle (w/ the top up)? Does it go back up when you close it all the way?
Check the drains to ensure they are clear but also check the window.
Let us know what you find.