I have a storage room in my apartment block (each apartment in the building has a private storage room in the basement). I suspect that someone may have entered there, maybe the landlord who lives in the same block, or another person who may have lived here before and could have kept one of the copies of the key.
I was thinking about changing the key, but I'm wondering if I can come up with an idea that would be cheaper and also could tell me if someone has entered.
A security camera would be great, but there are no power outlets (the electricity bill of the storage rooms is shared by all neighbours in the block, so they don't want people to plug certain electric devices there "for free" and there is only a light bulb with a switch). I could use a power bank like the ones used for smartphones but I guess it would only last a few hours. Also, the camera could not send the images anywhere from there.
I also thought of putting some object behind the door that would break when the door is open but I would also break it when I enter
Do you know if there is any clever idea for this or some device that I can buy?