Payment channel networks (PCN) enhance the impact of cryptocurrencies by providing a fast and consensus-free solution to the scalability problems of traditional blockchain protocols. However, PCNs often rely on powerful nodes with high availability and computational capacity, hindering their adoption in mobile environments. In this paper, we consider a hybrid PCN architecture that extends the functionalities of traditional PCNs to wireless resource-constrained devices. We analyze the token theft vulnerability and propose a countermeasure based on lock time windows. We evaluate our proposal with real data from the Lightning Network and from mobile broadband networks. The results show that the minimum lock time window depends on the downtime of devices and that selecting a default window is most effective when devices present high availability.