That sounds like a cover for a box where connections can be made to an antenna for TV or an audio system OR for an optional electrical outlet. Without a picture or seeing it, hard to tell for sure. Probably a minor external leak that is then collecting on the cover, then dripping out. We had one just like it in our pickup camper, and it leaked a bit in heavy rainfall.
6" of rain in the one night??? WOW!!! That is raining cats and dogs. Hope it's not too difficult to fix.
Erich Weinberg and Kathryn Whiting
Five Star DEF