Seems as good a place as any, I was just taking a shower and when I reached for the bottle of shampoo that still had a fair bit left in it and I had left upside down on the shelf above the shower it was all empty, that's funny, further investigation reveals all the shampoo had run out on the shelf because I? had neglected to close it properly.
Hmmm, I'm 50 now am I beginning to slip? this is very unlike me to not pay close attention to a detail. So after the shower I ask my wife if she had happened to be using my cheap shampoo instead of her expensive stuff?
Well lo and behold yes she had which explains everything