Water in the gas tank

Truck was fixed in December 2011 for water in gas. No explanation as to where it came from other than the gas station, which they denied. No one else seemed to have issues at this time. (Small town-800 people)This week, there have been 14+ complaints. Mechanic states that if it were an issue with gas station, others would have also had problems, which is understandable, but we are still wondering how this could have happened. He checked everything else over that may have caused it, and no issues were found.