Well, the AIM-4 Falcon could do sorta that; it was carried internally in interceptor's weapon bay, and interceptor fire control system aligned its seeker with target & set the range gate while missile was still inside. So by the time missile got launched (it took about 1.5-2 seconds, so likely classify as ejection), its seeker was already locked on.To do this, you need to "capture the target on the trajectory", there was definitely no such thing on old missiles with IR seeker
So by the time missile got launched (it took about 1.5-2 seconds, so likely classify as ejection), its seeker was already locked on.