Just get the coat hanger and fish that cable out. That's my last resort tool for issues like this.
For future reference, if a chain stay and BB area has ample room, I would just use the plastic cable sleeve to guide the RD cable through. For the RF25/G056 frame, I don't even think I bothered with the magnetic cable tool.
I was using the white plastic cable to guide the shifter cable but the it couldn't pass through. I thought there was a weird bend so tried from the other way (from the bb) and it got stuck.
