I lost an auto rifle frame after mistakenly applying its radiant matrix to the Gofannon unlock questline's sniper frame, and attempting to forge both at Gofannon. The sniper forged on ignition but the other frame was removed without giving me the gun. I'm aware that this is a known issue, but I'd also like some assurance from Bungie that our lost frames will be replaced? Additionally, the fact that the radiant matrix can be applied to quest-based frames seems like an issue of its own. (Also: this failed to post due to a maximum of six tags being allowed... with only three tags (lost item; gofannon forge; black armoury) added. Might want to look into that - seems to be counting the automatically-added tags without showing them and splitting tags with spaces into separate ones.)
I just had the same thing happen. Had both the auto and sniper frames, forged the sniper and lost the auto. I had heard there was a glitch the other way around, which is why I forged the sniper first.