Actully you can check if he opened the chest or not yourself, just get a iron pickaxe and right-click on the ground under or next to the chest it should show up something like this:
Clicking again will show another page of logs, so you can go back in time even if you have opened your chest a ton.
Also if your chest does not have a private sign on it then it's free for anyone to open, what masy said:
masy1 Wrote:Just because you made it, doesn't mean that it is automatically privated....
You have to right click the chest with a sign and the sign will say
[Private]
xTheEliteZx
Then you know that it is privated...
If you don't know or aren't sure if it is, just punch it (left click) and it will tell you if the chest is privated or not.
it should look like this:
if you need any help locking chests, adding extra names to the signs ect watch this vid:
https://www.youtube.com/watch?v=m8EHAT6BZ-g