Erase event will remove it from the map, but it will not erase it from the game, so when you leave and re-enter the game will reload the map as normal and see that the event should be there and place it back.
It's the same reason why events don't remember their move-routes after you've moved them, exited and reentered a map.
To remove (disable) an event you need to use a self switch, which are saved to the game. Instead of erase event, turn on a self-switch and then make a new page for the event; you then need to set the new, empty page to depend on the self-switch that you turn on in the first page, which is done with the top-left conditions in the events editor.
Making the event reappear again is a bit more complicated as you'll either have to use a script to go inside and switch the self switch off or use a global switch.