A new efficient preamble-less short frame, called Quasi-Cyclic Short Packet (QCSP), has been recently proposed for the Internet of Things (IoT) deployment. It has demonstrated its good performances in the process of detection, synchronization, and error correction in an asynchronous Additive White Gaussian Noise (AWGN) channel, with residual frequency offset, and at a very low Signal-to-Noise Ratio (SNR). The detection process uses the normalized score of a non-coherent frame match filter to assess the presence of a frame or not. In this paper, we improve the detection performance by combining noncoherent detection with coherent detection. The proposed method decreases the probability of miss-detection by two decades, for a given probability of false alarm.