First of all - renting your timeshare, collecting the money, and then cancelling the reservation would be a criminal act, and since the renter and the resort have all of the owner's info., it's not something they can get away with.
However, I tell my renters who are nervous about this happening that they can call reservations once a month, a week before check-in, and the day before check-in, just to be sure the reservation is still in their name.
In reality - renters have nothing to worry about with legitimate timeshare owners - they have too much to lose.
The people you have to worry about are the rental scammers, who don't even own timeshares. They are advertising bogus reservations on the internet for rent, that don't even exist. When you ask them for documentation, they will either send you a photoshopped reservation, or disappear.
Using the rental procedure recommended on TUG will protect you against the scammers.