toilet training set back

[sez88]

Hi everyone.
Charlie has been going to the toilet outside (as opposed to on paper or on the carpet) without fail for just over a month.
Last Sat we went for a holiday in spain, when I got up the morning we were about to leave he had gone to the toilet on the floor in the kitchen.
My sister and her friends have looked after him this past week and have told me he went to the toilet outside as usual.
We arrived home early this morning to a very excited pup and had a normal day with him. Just now though as my sister was about to leave he urinated on the carpet, I have no idea why, the backdoor was open and nothing was in his way.
Confused!!

Any ideas why this could be?

[Mattie]

Take him back and retrain him to potty outside, it won't take long for him to realise what you want him to do.