Dementia and stoma, how do we keep Dad from disconnecting his bag?

My father has a stoma, due to bladder cancer. He also has dementia, which has recently become worse. Up to this point my mother has been able to care for him. Recently he has started disconnecting his night bag from his day bag but forget to put the plug back in. My mother has even tried taping the connection together but he still finds away. Up until recently he was able to unhook himself and plug in the drain. My mother is about at her wits end--cleaning and washing daily. Any suggestions how to keep him from doing this.