Why didn't Alex just tell his mother when he found the chip?

Remember when Alex sent the car around with the camcorder on board filming? When it returned to his room, the tape had been taken out. Alex then opened up the car and found the chip that was hidden inside.

At that point he phoned the Army Recruitment Office. The person he spoke to said "lots of toys have Army on", and sounded annoyed with him. Anyway Alex read the number on the chip, and the person from the Recruitment Office must have relayed the message to somewhere else, because later in the film someone said "We've had a message from a kid in Chicago about the dangerous chip".

Having been told off for the two so-called "false alarm" 911 calls, why didn't Alex just tell his mother when he found the chip? His mother, as an adult, would have been in a better position to tell the police about the chip at that point.