Depends on how old you are. If you're over 40, then yes, this is illegal discrimination. If you're under 40, then while it is discrimination, it's not illegal discrimination.
No so fast - if this were the reason that the OP was denied employment, then it would be illegal discrimination if the OP is over 40, but the OP is vague.
The MANAGER of the store expressed his preference, but he didn't make the hiring decision. Additionally, we have not second-hand, but
third-hand information about this matter. Furthermore, there doesn't even seem to have been any sort of applicant/prospective employer-type relationship between the two parties.
Of course, it could just be that the OP was very vague and didn't state the details about his matter very well.