A lesson learned

I can't remember how long ago this was... I'm guessing Trevin was about 2 1/2 years old.
One day we heard Trevin say " Oh My _ _ _." I kind of blew it off cause I wasn't sure if that was really what he said. Well later that night it came out again. So we sat down and talked about how that was a bad thing to say, Heavenly Father doesn't like it when we use his name a bad way, etc. Trying to tell him in a way that he would understand. (We thought our kids would be a lot older when we had to cross this bridge.) We didn't hear it for a few days, then it happened again while Gage was around, and Trevin was scolded a little more strictly than the previous time, which resulted in the same thing a few days of it not being said and then it returned. So we decided that during Trevin's night prayer we would help him pray "to not use bad words." So we did that for a few nights and things were better. It was a nice gentle reminder at the end of the day to not say the bad words. Well a few nights later Trevin wanted to pray without help... Awesome right!  Well his prayer went something like this...
"Dear Heavenly Father, we thank thee for this day. and our bed. and our toys. Please help us remember not to say "Oh my..." because saying "Oh my..." is bad words and it makes you sad when we say "Oh my ..."  so we won't say "Oh my .." any more. In the name of Jesus Christ, Amen."
I guess he learned the lesson, kind of...