If they are functioning properly, airport scanners have no effect on magnetic media. They are X-Ray scanners that look throu things. X-Rays can fog film if subjected to reptitive exposure,. I have traveled quite a bit the past 10 years with magnetic media - laptop, digicam, etc., and have never had a problem.
If, however, the scanner is not functioning properly, and is emitting a high level of collateral EMI, then it is possible to have some effect on magnetic media. But, I have never run into this. Then again, I have never traveled into and out of Mexico by air lately.
Can he read his pictures in the camera? If so - then the problem could be the reader used.