I think every Basenji we've had has gotten out. One forced his way out a second story window, climbed onto the roof, and jumped off. Another zipped past me when I opened the garage door literally a crack and she went after a cat. And one literally took off as the garage door was closing, slid on his side to get under it, and then took off. Then there was the one who darted through the slats on a deck and jumped 15 feet in pursuit of a cat. He also got out when the maintenance man opened the door to our temporary apartment without knocking. And oh, the one who jumped the fence in the park with a partner in crime and ended up at a Mercedes dealership.
All of these ended up without incidence. A neighbor collected the one who jumped off the roof -- at 16 BTW -- and came over, range our bell, and told us she had our dog. And we were ???????. LOL The one out the garage chased the cat into our neighbor's house where I collected her. And the one who skidded out the garage door ran around the road which circled our neighborhood -- with me shortly behind in a car being directed by everyone on the street -- until he came back home where he waited for me in the driveway.
The point being it's virtually impossible to ensure these guys don't get out 100% of the time. This is why it's best to practice recall before you need it. And if in doubt remember that running in the opposite direction and starting a game of chase is a good way to have them come back pronto.