When India was partitioned they were three provinces which were split based on religion: Punjab, Assam and Bengal. However, there were other provinces/states which could have been split based on religion, one of them being Sindh. Sindh, being a Muslim Majority province, it was going to become a part of Pakistan anyways. However, it had (and still has) a sizeable Hindu population, even making slim majorities in some areas, as evidenced by this map:
However, something worth noting is that the Hindu majority areas in that map is desert, so you might have to ask yourself: Would Sindhi Hindus, most of them living in urban areas such as Karachi, would they be willing to uproot themselves to a sparsely populated land with barely any resources? Of course, there is also a possibility that Sindhi Hindus would just skip Indian Sindh and move to an urban area such as Delhi or Mumbai.
I wonder why Congress decided to play the same game in Sindh the Muslim League was playing in Assam, but I am guessing it is because they wanted to portray themselves as a secular party and demanding such stuff would hurt that image. However, the option to do so was still open. Could Sindh have ever been partitioned? How different would the subcontinent be in a partitioned Sindh scenario?