legal question about property

Please advise.
I purchased a house on April 1, 2013. The seller wanted to stay in the house for 2 1/2 months until his new house is ready. We signed a rent agreement which including he has to maintain the property as original status. There is a Volley ball court on the property which is included on his upgrade list and apprasal report. No clear statement on the purchase agreement. Last week the original ower (now the renter) sold the Volley ball court on Crig list. We have discussion about who own the VB court. Not able to reach agreement. He stated that belong to him beause it is removable. I said it is mine because it appraised in the house price. What should I do next? Small claim court or arbitrition?