2001 Dodge Ram Oil guage

I hit a small speed bump and when I did I heard a "ding" and a lght on my dsah, stating check guages, came on and I then noticed that the oil guage was not getting a reading. I change my oil as scheduled and I have oil now. After checking the oil, I started it up and the guage had a reading. After a couple of hours, I drove it and had no further problems. What could this mean? One frined said the oil pump another said a loose connection to the oil sending unit? Are either of these things likley?