I have a lexus rx 400H..has 33,900 miles. I was told the tire sensor is bad?

The check system light came on and all the tires check perfect pressure but one of the tires they cannot detect the sensor and DISCOUNT TIRE is saying that it is bad. Now my questions is: These are new tires with about 2,500 miles on them. Could the sensor have been damaged during the installation of the tires? The check system light just came on? It has been 2 1/2 months since the new tires were installed? One thing to mention-I did have them put 2 pounds more of air in the tires, but now the air was taken out because we thought this triggered the check system indicator, but it made no difference. Any thoughts on this. Could discount tire have damage the sensor in some way. OR, does the Lexus tire sensors have a short life?|||Things break in a car. 2 and 1/2 is a long time. If they broke it the light would have lite up then.|||If they damaged the sensor it would of showed up as soon as you drove it away. Two pounds extra wouldn't kill it either. Is it covered under warranty? Lexus will take off the tire and tell you if it was damaged or not. Either way you think you should be covered.