Once you have eliminated the impossible, whatever is left, however improbable is the answer!So, either the neighbour came in and did this [improbable but not impossible]or you somehow did this yourself, forgetting the alarm and switching off the power point and then forgetting.Or, there was a power cut [although that doesn't account for the switch being turned off.]Sometimes I could have sworn that I had done something [or not done something] that turned out to be wrong.Next time you go out, have 3 things to do that you switch on in the house, then come home and see?