I'm only able to trigger this on a server but there is a chance when firing a missile from a launcher using a laser designator while the launcher is unloaded that once you return to the launcher the launcher will launch its missile but the missile will never be removed from the launcher.
This is not a visual bug as i can take the missile out.
Used ICBM version: Self-build until this commit: a5d481c
EDIT: It turns out that these missiles are not always physically present within the launcher and cannot be launched unless you take them out and put them back in.