@Heidy27
Yes, well, it happens. It always makes me wonder why anyone would bother. I think it's often just a mistake when rushing to pack before their flight.
But what caught my eye and compelled me to post a response is your mention of "slovaks", because the last guests we had where towels went missing were... Swiss. Yes, really. About a year before that, towels went missing after a German family. A really nice German family.
I don't think nationality has anything to do with it. It's either a character issue, or just inadvertent negligence. Has nothing to do with nationality.
But yes, it happens. Sometimes. Well, rarely, really. Nature of the beast.