No, no, I totally understand! People going for an al fresco dump and either leaving it open, or putting a stone on too, is a particular annoyance to me...especially in climbing areas (by climbers too!). I usually carry a trowel, but have mainly just done a dump in the plastic bag I carry it in, as that's usually the easy option to carry out. Works for dogs, why not us? There's currently a massive thread on UKC (climbing forum) about this, and I am amazed about how many ruffty tuffty folk are very squeamish about this.
And relax.