Volume option disappearing so will not let me change volume!

A few days back my iPhone 4 fell in water, to which I quickly took out and placed in uncooked rice for 24 hours. Once I took the phone out of the rice after 24 hours everything seemed to work fine...but...the volume buttons on the side do not work and when I go on music there is no option for the volume to be changed?!

After some research I discovered that if I go on settings > sounds I will be able to change the volume through there to which is DOES and the speakers work.
This is a very strange problem because it seems that the volume buttons are working but will not let me change when not on the settings page etc

I've tried to cleaned the headphone jack and the charging port and even restored the phone but the problem is still on the phone
What do I do?