Most of my guests are driving and take their tatty pillows with them to sleep in the car. However I’ve seen more than one bring in what looks like sheets and duvets. I used to travel with paranoid friends like that. It’s funny since my linens are almost certain to be cleaner than what they drag in with them.
I suspect that my guest might have drooled in their sleep in embarrasement taken the wet pillow and replaced with the dry and then dried the cover with the blow dryer.