I feel really bad now. I bumped into a colleague who was with her 2 year old and asked her in for a cup of tea. found a couple of toys from my almost grown up kids and her child sat on my (posh wool rug playing with them while we had tea. Pool then formed and it was clear that child had done a rather large wee. Mother was apologetic and said that she lets them go without a nappy but not potty trained yet. I mopped it up and later scrubbed etc, unfortunately you can still see a circle in the geometric pattern which is a different colour. Is wool and natural dye and honestly not sure it will come out. It does not look terrible but you can see it and it is in the centre of the room. Saw her today and she said, oh I hope it came out of the carpet OK. In the past I would just lie to be nice and say, yes it did, no worries, but these days I am a bit more honest so I said, not completely actually but it's not a big deal. She looked worried and apologised again and offered to replace the carpet. Of course I said no, but now I feel really mean and guilty for being honest about it and not just telling the white lie. On the one hand I think she should have been a bit more careful and on the other hand I don't want to be precious about it as of course 2 year olds make a mess, it is not the kid's fault. Obviously there is not much to be done now other than neither of us ever mentions it again, but AIBU to be slightly pissed off?