Forgetful is fine. Also absent-minded could be used. Dispelled is entirely wrong in this context. Dispel means to correct or disprove an idea or belief that is factually wrong. ie If I said to you that I believed everyone can speak a foreign language you would very quickly dispel that incorrect belief. Oblivious is also entirely wrong. If I was in the kitchen of my house and my dog was in the bedroom, chewing my slippers, I would be oblivious of that. ie unaware of what is happening.

In general I use forgetful. Some use the two interchangeably. I think oblivious as more not caring about others and do what they want. Example: I was forgetful of the food I was going to take to the party because my kids were fighting. (As if you have too much on your mind.) My brother frequently calls me at my kids' bedtime oblivious to the fact that there is a 2 hour time difference and that we are busy getting ready for bed at a certain time during the week so I am unable to talk to him then. (he calls even though it isn't a good time for me or whatever the action is.)