Thank you Claire for your kind help.
I am afraid I did an immediate restitiution, thinking that it was a message going to Airbnb, not to the guest. As the program forced me to fill out an amount, I indicated 50 euros adding in the chat box that I was only filling out that amount to get through with my message. I basically just wanted to ask Airbnb what was reasonable. I never felt it was reasonable to want to buy a new matress because someone peed in it.
But now that the urine really sank all the way through the matress over the hours that passed, I start to feel that perhaps it would have been reasonable to ask for a new matress.
Next thing I saw was that the message went to the guest immediatly. Asking for 50 euros. And no reaction all day. So I am not hopeful.
My next problem is, however, the guests that arrive tomorrow. Where will they sleep?
I am trying to call airbnb, but the phone voice tells me that I will be charged for the call in the US. I am making this whole thing even more expensive. There is no Belgian number (Belgium is where I live). There is a number in the Netherlands, but there I do not get an answer. I am expecting a family of three tomorrow, really nice people....
I never put in a security deposit because I worried the money would be withdrawn from the person's account as if I did not trust them...