Denis bought a diamond ring on credit from Pavel as an engagement present for his fiancée. He signed a purchase money security agreement giving Pavel a security interest in the ring until it was paid for. Pavel did not file a financing statement covering its security interest. Denis filed for bankruptcy. The bankruptcy trustee claimed that the diamond ring was part of the bankruptcy estate because Pavel did not perfect his security interest. Pavel claimed that it had a perfected security interest in the ring. Did Pavel have to file a financing statement to perfect its security interest in the diamond ring?