A tip I have for everyone is to be aware and always check what you got everytime opening chests. sparkles and the like, if u realize is a key item, immediately check if x25 is on(DO NOT accidentally tap screen again it will force an autosave and then nothing can be done). and if it is somehow on, your account can still be saved if u immediately turn off x25, turn off internet and force stop app in settings as well as CLEAR CACHE. This Does Not work on main story chapter 52 specter palace key. Then open game with internet and all should be fine. you will resume at previous autosave (some steps may not be necessary but i recommend doing it all or testing on a non key item as mechanics should be same. This is especially useful for when you randomly get a key in places you don't expect such as dialogue. It can also be applied when you see some rare item like light or shadow but u realize you have x25 off