I never saw the movie, but since discovery by SAR is unlikley, water is short and there are no nomads in the area, it seems reasonable to travel hoping to make it to a more favorable location or to increase your chances of running into other people that might also be travelling in the area. That beats sitting at the crash site forever with no one coming for you. The crash site would still be a target for possible SAR efforts and you would leave information about your direction of travel for SAR to follow. Most importantly, your chances of finding water would increase if you moved. Navigation would be tricky without a compass, but alternate methods would have to be used. Maybe using the sun/moon/stars or distant mountains to hold a heading.
I would prefer sticking together, but if there were a large number of survivors and the group seemed to be polarizing into two cliques, either around two rival leaders or two ideas of the best course of action, then splitting up would be a possibility. Splitting could reduce internal conflict and increase the chance of being discovered. But in general and especially if the number of survivors is small (less than 10), I think sticking together for mutual support would be the better option.