According to Facebook user Buhari Sallau who shared the story, President Buhari's official driver, Sa'idu Afaka, found a bag containing huge sums of foreign currencies that someone misplaced and returned it to the proper authorities.
Read according to the source below...

"PRESIDENT BUHARI'S DRIVER FOUND MISSING MONEY IN SAUDI ARABIA AND TENDERED TO AUTHORITY!

Impressively, I am proud to report that Staff Sergeant Sa'idu Afaka being the Official driver of President Muhammadu Buhari who is currently undergoing Hajj operation in Mecca, Saudi Arabia has found a bag containing huge sums of foreign notes including US Dollars and Saudi Riyals that got missing from someone. When Afaka realized it was money, he quickly looked for authorities and submitted the bag to the Hajj Commission located at Ummul Jud in the city of Mecca and demands they should please look for the owner. It was when he brought the money to the authorities that they all realized that there was an International Passport of the owner of the money.
WOW! CHANGE IS TRULY HERE AND THIS IS COMMENDABLE!"

http://www.lailasblog.com/2016/09/president-buharis-driver-reportedly.html?m=1

Story story

Make I hear, even Goodluck driver also found some n returned it