Hi Chris and Julie.
As Gill says, getting to the root of inappropriate toileting can be difficult, as a number of things could trigger it. Did anything change in the household in the immediate time before this happened? Cats will sometimes per on our belongings because they're stressed and are marking the items which they associate with us. Personalizing the stuff, helping to reduce the stress. It may not be immediately obvious to us what it is causes our cats to act this way, so we have to observe keenly our cat's behaviour and note anything which seems different.