Unless it was changed, a script placing down a locked chest will belong to nobody (not even the person who ran the script). You can get around this by making that gives a player a history and once they player has it, the next person will get a different history.
Ex.) chest1, chest1, ect
I tested this the other day when my friend asked me to try it for him. It, in fact, does work now. I'll add that script to my directory and you can check it there! Only reason is, it's one not on there, and no use in writing it twice. The directory is in this section of the forums near the top, can't miss it.