honestly the gas has nothing to do with missing your cycle. some people get gasy right before a period because they tend to eat foods that they crave and it happens to be gas causing food. It means that you need to keep an eye on the calendar and if still no period after a week buy a test and keep an eye on what your eating that could be causing the gas.
Not to sound like a smartass..... but it just means that you had a short period this time (if you meant to say that you only had a period for 4 days) AND that you've got gas. One really has nothing to do with the other - bloated, yes, that's menstrual. But gas, no, that's intestinal.