Considering the significance of mobile-Wireless Sensor Networks (WSNs) under Low Power Lossy Network (LLN) Conditions, in this paper a highly robust and QoS-Centric Fault-Resilient Routing Protocol for Mobile-WSN in LLN (Q-FRPML) has been proposed. Unlike classical routing approaches such as Routing Protocol for 6LowPAN based LLNs (RPL), our proposed Q-FRPML protocol contributes multiple novelties including received signal strength indicator (RSSI) based mobile node positioning for fault-resilient communication, proactive node management, RSSI and ETX objective functions based best parent node selection, link layer adaptive fault-resilient alternate path formation for QoS centric communication over mobile-WSNs. Q-FRPML protocol is implemented in parallel to the link layer of the classical RPL IEEE 802.15.4 protocol stack that once detecting any link-outage executes best parent node selection and alternate path formation to assure reliable data delivery. In this process, Q-FRPML avoids continuous network discovery that significantly reduces signaling overheads and energy consumption. Contiki-Cooja based simulation results have revealed that the proposed Q-FRPML protocol outperforms state-of-art native RPL or S-RPL protocol in terms of higher packet delivery ratio, lower packet loss ratio and end-to-end delay under varying network or load conditions. Though, Q-FRPML protocol has been applied in parallel to the native RPL, it preserves backward compatibility and hence can be applied in real-time mobile-WSN based QoS centric communication purposes.