I did some googling, too... I have to admit that I am surprised, because apparently such a ship (run by Tylos) HAS operated almost within the last decade, namely 2001... but it was stopped after just 3 voyages (and it was described somewhere, that the ships standards were more like those of a cattle ship LOL)!
And then I also stumbled on this (dated March 2006):
Marco`s Dubai-Kochi luxury liner service from mid-April
...and this (October 2005):
For me, it makes sense, that if there is a passenger boat service, it´ll go to Cochin (South India), because from that region, especially Kerala, thousands of people have gone to work in the Gulf states.
So, nothing solid, but just may be this ain´t as far fetched, as I first thought. Even though generally in Asia long-distance passenger ferries are a thing of the past. In the articles it was said to take 3 or 4 days – you don´t have many ferry lines that long operating even in Europe any more!
I would think that some travel agent in Cochin or elsewhere in Kerala might know, if any such line is operating now, or if there are plans to open one.