Fire trap's damage values definetly don't get increased by spell damage. When I remove my wand with 48% spell damage, fire trap's damage stays unaffected. Fire damage and elemental damage seem to work though.
Edit: It actually works in "C" stats but not when you hover over skill icon bottom right. For my other skills it shows same damage value there and "C" stats, but not for fire trap. So it's just an inconsistency issue.
Fixed, thanks for bringing this to my attention. It was filtered on the popup incorrectly.