Another soiled mattress - guest check out without informing me

Even the best mattress cover won’t help if someone takes it off. In December I found a stain on the mattress cover & think this doesn’t look like what I purchased. Remove it & find a coffee spill.

As best I can tell:

  1. Guest stained original cover & removed it.
    2 either they or another guest spilled coffee on unprotected bed & purchased a mattress cover to hide the stain
    3 another guest stained the replacement

Do people do this in their own homes to their mattresses?