alberta ~ is it possible that what you saw was not the mucus plug? They have quite a bit of discharge towards the end, is normal. When is your cow due? Lots of movement is normal, usually baby slows down/quiets as it gets closer to birth. I would not be concerned unless your cow is more than 2 weeks over due.
How about the other signs of calving, How is the bag, the teats are they full looking or still sloppy? Has she fallen?...around the tail bone, is it soft. My husband says the cord is normal when it is tight like a fiddle string...I have a hard time with this unless there is a visual difference. I tell by the bag, the attitude, wandering off by herself, the crook in the tail, tail off to the side, (it does not cover the poop hole, hangs beside it), and crawling the fence line.
I've had cows start to "string or stringing" muscus 30 before they calve. Every cow is different, some won't string much at all, some bag up a few days before calving and some just hours. All you can do is keep an eye on them and watch for signs of labor.