The Raise Zombie spell casts an FF Aimed effect, but since it's a reanimation it seems to add the effect to the caster as well. So I changed this reanimation effect adding a script that decrease the caster's magicka while the effect in on. It just contains Caster.ModAV("Magicka",-10) at start, and then Caster.ModAV("Magicka",10) when the effect finishes. And this is working great.

I tried to reanimate a body, and my magicka was correctly decreased. Then I saved the game while the body is reanimated, quit Skyrim, unchecked my mod in Data Files, and finally came back loading the save. My magicka was obviously still hindered since that initial ModAV was not restored yet. However, to my surprise, when the conjuration was gone my magicka was correctly restored to the original value, even with the mod unloaded.

What I want to understand is: how is this possible? How can the game know there is a scripted ModAV("Magicka",10) at the OnEffectFinish of the reanimation effect, if the mod that inserted this script is not loaded anymore? Does the savegame file in some way store the modified effect on the player and keep that information even after the mod is removed?

http://www.creationkit.com/Save_File_Notes_(Papyrus)

There are a couple of threads discussing the "save game features" of Skyrim.

You disabled the esp but are the pex script files still here?.

Yes, I'll try now to disable the esp and also remove the pex. That's probably the answer. Thanks.