Some keys on my 9900 keyboard suddenly not working!

Ive bought this 9900 few months ago second hand. theres no problem with it except for the battery but its fine in general. I was just texting few hours ago, then just left my phone on my table why im using my computer. Its literally just there, i didnt touch it. suddenly when im about to text, some keys arent working.

the all the vowels arent working. and the q key.

OK HOLY @@# I was testing the keys one by one so i can specify it here... then suddenly i can type the letter I... then one by one it magically worked again! WOW (i put my phone on uncooked rice few mins ago by the way maybe thats why?)

ok so now my question is, why did this happen!?? and how can i prevent this?

Only you can know what happened to it. As phones just dont STOP working for no good reason. Maybe it was too humid in your area where you were? Maybe the phone has residual water damage? Maybe you need to replace the keyboard? Keep an eye on it and treat it as you did last time.