He stated this in Abuja during a book launch titled, 'Muhammadu Buhari, the Challenges of Leadership in Nigeria,' written by professor John Paden.
The former president recounted the days Buhari served under him as commissioner.
He said: "President Buhari and I have had many encounters, but most of them in parallel. Not too long ago, we had a direct opposition at the ballot box. But even then, it did not affect our relationship.
"And fortunately, we didn’t have to look at each other through the barrels of our guns. I thank God for that.
"On one occasion when President Buhari was a commissioner for petroleum, he went for an OPEC meeting in Saudi Arabia, and each leader of a country was given a special gold coin. President Buhari, then an army officer, came back to show his superior the gold medal which was very expensive, and said: ‘This I was given, if I give you, promise me that you won’t give it to somebody else.’
"And that came about because one of his colleagues bought me a hand-made shoe, and after I discovered that it was too luxurious, I gave it to my ADC. I believe President Buhari heard about that story, and he wanted to make sure that I didn’t give out the gold coin… But don’t ask me where the coin is today."
The audience at the launch were said to have erupted in laughter at the remark.
In his vote of thanks, Buhari reportedly identified the officer Obasanjo referred to as the late John Garuba."
The biographical book chronicled the struggles and career of Buhari until May 29, 2016, when he assumed office as a democratic leader.