I mean, "is x divisible by y?" is only one aspect of fizzbuzz, and something that can be solved in many ways - you don't have to use the mod trick. You could write a function that uses a loop and subtraction to do that bit, if it comes down to it. If I just want to see you can code I'll take it and move on, and if I'm at a point in the interview where I am looking for something else then that's a conversation starter.

But if you are applying for a programming position and claim a decade of programming experience - and literally can't come up with any path towards a solution - I smell a rat.