Mystic forge destroyed items on exit.
Any chance you clicked “Deposit all collectibles” at any point during that? They added depositable slots for shards, ecto, and coins, so they may be back in your bank if you deposited any mats you got from the forge when you went to buy more stones. Not saying this is what happened, but I’m in the habit of doing that and with the new collectible slots, that happened to me yesterday.
That is exactly what happened. I cleaned my inventory right before I bought the stones too. Did not know that was there thanks.