Same spell, different ID?

[Malsomnus]

I've had a user complain that my add-on has the wrong spell ID for the Guard (the monk ability) and Resolve (the tank thingy) buff. According to him the add-on doesn't work correctly, but it's fine after he changes these numbers in my code.
That's all good and fine, except that the add-on definitely works as intended for me, showing both buffs correctly.
Is it possible that these buffs use different spell IDs on horde/ alliance? Or is there perhaps another perfectly logical explanation for this?