I encountered this twice in 2017 and once earlier this year. There would be a booking for a large amount, say 4 or 5 nights, all case with a cost of more than $1,000. The guests would not show up and we find out on arrival date that the phone number is invalid (or belongs to some innocent person) and the credit card is declined. I have also experienced this a couple of times through expedia.
I have recently begun validating credit cards and, if they fail, I make a phone call. I just caught one just this morning.
I'd like to know if anyone else has had this problem and what have you done about it.