My moisturiser has been going down faster than usual. The 13 year old denies everything

I opened a new jar at the start of the month. It is half empty and I have been using it as normal. My daughter keeps her own things in her own room. My son walks past smelling faintly of rose and says he has 'no idea'. I have decided not to solve this. I will buy him one of his own and leave it on his shelf without a word.