[Angelox]

Right - Chanters always had the "pet go away" option; and all casters had to develop AA's as to be able to invis with the pet, if not, the pet would poof on invis. Also, all casters had to earn AA's that would allow them to "suspend" the pet so it would not get lost on zoning or camp out.
Enchanters could also develop AAs to assume control over their pets (/pet attack, etc). I played for a very long time with my enchanter and had developed all these AA pet skills.
On the Dire Charm AA (think it was called that), if you invised, the pet would break charm and attack the charmer.
Reality is, pets should poof on invis, and also poof when zoning or camping out, unless you had the AAs.