Damn, that happened to me 2 days ago! The object ball I moved moved less than an inch, then the cue comes around and barely nudges it and freezes to it. I had made the shot and asked my opponent what to do. Since I was hooked beyond hooked he just gave me a sly look and said "looks like your shot!".
Hey... What if the cueball crosses the path where the object ball would have been had it not been accidentally moved? Sounds to me (from your OP) that would be a foul.
Yes that is a foul.
BVal