After upgrading networkmanager my modem disapeared.
[2018-10-22 20:45] [ALPM] upgraded networkmanager (1.14.1dev+13+g0d323447-1 -> 1.14.3dev+15+g3fc59221-1)
Arch linux. Nothing else that matters changed. I use
Bus 001 Device 020: ID 12d1:1506 Huawei Technologies Co., Ltd. Modem/Networkcard
modem and it worked fine before i updated and after i rolled back. But on version 1.14.3dev+15 modem just didn't show up in nm-applet nor it worked via npcli. If any other info required just ask me.