Well if I was in your position there would have been no dragging it around my house and no stinking out the playpen and sleep room because I would have just thrown it straight in the wash as soon as he arrived. It isn't our job granted but whatever, its in our best interest and really isn't that big of a deal. I would tell mum she NEEDS to cut it in half for this exact reason as it is understandable that she couldn't wash it in time for daycare after an accident, but then she can not bring it to daycare as it is unhygienic and inconsiderate to everyone. Cut in half there is half at your house and half at hers and then there is no issue of this occurring again in the future. I would make it clear that it needs to be in two pieces for tomorrow morning at drop off.