Too bad you already had a guest certificate on it, otherwise I would suggest you just rebook it, provided there are smaller units and larger units, as you and I have both heard about some inventory that when cancelled does not return.
I suspect there is a delay on cancellations, as it might hold the cancellation until a sweep for upgrades is ready to run. But I don't know. That could be one reason why cancelled units have not come back. It might also be a way for Wyndham to discourage the C/R by making Cancellations not returning immediately, but with some degree of randomness. Who knows, just speculation until more examples are provided.