Non emergency police is not OTT if the OP can't sort it out with the CM.
If the CM continues to lie and pass of the ticket as real then she is committing fraud and so brazenly too.
Who would knock up a ticket like that, honestly? If the CM screwed up - wrong child going, got days mixed up etc she could've been gracious enough to refund and take the hit herself to save herself from upsetting a client and getting a bad reputation.
She didn't and now she is considered untrustworthy, a liar and a thief and has indeed committed fraud and obtained cash by deception.
There were many opportunities for her to come clean about this. The OP herself had left the door wide OP for her to be honest with her first line of enquiry about the trip
So yes, I would call the police and I wouldn't feel shit or OTT because if a person could so brazenly do it to me and create false flippin' evidence then she could do it to someone else who doesn't have the strength to question it.
As for safeguarding. Yes it is an issue. She was meant to be in X place but was instead at Y. What if a parent needed to collect early or there was an emergency? There's a reason you plan these things and unless the absolute extreme happens you don't change plans. I'm sure under her insurance there are risk assessments and gawd knows what that she'd have to do (I have to do it just to ensure my insurance will pay out in a worst case scenario)
So as petty and small this appears there are repercussions that are much bigger for the OP, her DS and any other children in her care.