I would go for justice. Karma is supposed to effect someone in their next life.
Agree. Karma is very often misunderstood in our community. Justice and/or a spell to return the lost object would make much more sense.
I am sorry to learn you have been stolen from, did you report it to the Police? Was it insured?.
If you are the kind of pagan who would "harm none", then working towards the return your item would be the way forwards.
If you are the kind of pagan who isn't strictly a "harm none" one then maybe working towards teaching them the error of their ways may be a better way to go about it.
I cannot advise you more directly without more information about the situation and your beliefs/practices.
I generally stay completely away from anything about stealing things. Spirits are really stupid when it comes to objects and your just as likely to get some really bad :returns from them as getting them to do anything when it comes to stealing. Basically I have had numerous greys etc steal and relocate drugs and keys in my life and it seems to take them hours to get over it.