My husband has 50/50 as well. Whenever mom decides to not bring the child back, he files a police report. We have been told by our lawyer that you'll have a better chance of getting a contempt conviction if it has happened on more than one occasion (3 times is the general rule). So I would document it with a police report this time but not necessarily file contempt against her after just this one time.
Basically, with contempt, you are asking the judge to resolve it when the CO isn't followed. If mom denies visitation but then gives you the child back, then generally, the situation has already been resolved because you got the child back. So when you're trying to file contempt against someone for denying visitations, you want to be able to prove that it is a habit and not just a one-time thing. A judge isn't going to want to spend the time hearing a contempt case just so they can give you one make-up day, but they will if it's like a week's worth of time.
We filed contempt after 4 denied visitations, but ending up dismissing it because a GAL was hired (it would have been pointless to then go to court because, ideally, the GAL would be able to resolve any upcoming visitation issues). Even though we didn't get an actual contempt conviction, we can still use those denied visitations to file for primary custody, which we have done now that there have been 4 MORE denied visitations (among other things - I'm not saying you should file for custody based on denied visitations alone).