well it depends on how he meant "A minor scale". If he meant it as 'a minor' or 'C Major' key then hes just dumb.....he coulda meant like 'a minor scale' as in any minor without the b? in which he could mean a#.
only 3 major scales have a# those are B M, F# M, and C# M. most peices are written in it relative minor. But thats suggesting hes a smart ass.
However every Major in flat above C M (F, Bf, Ef, Af, Df, Gf, and Cf) has a Bf in it. So using the realtive minor he either accidentaled all the Bf's too B nautrals or wrote in A#'s
...dependin on which key he used and the appropriate steps he probably created an asceding melodic scale...
Its been so long since ive used Music Theory and i've prolly forgotten alot
but thats what i can think of