I'm not sure if this a bug or not but about 3-4 days ago I used the Summon Pixie spell on a Couch Potato seed and the PIxie is still not going away after the 48 hours. I have come up with a theory about why this is:
1. This particular Couch Potato was constantly going into a wilted state after one night with the Pixie still flying around it and every time I corrected it's needs the Pixie would disappear and then reappear when It would mature.
The central 101 wiki says couch potatoes attract pixies on their own. Mayhaps your summon pixie spell and the plant attract kind of crossed over on the times they were there. Is the summon pixie spell still a ginormous amount of gold?