I think you're misunderstanding part of my post, maybe I didn't word it correctly.

The chiefs kicked the field goal at 1:23, 4th and 6 from the 15. Say they had simply got the first down and not a touchdown. There's a good chance that clock runs way the hell more down, and also a good chance you'll be forced to use the timeout anyway (through injury or tackle in bounds).

And now, your onside kick has to be 100% successful, because so little time will be on the clock.

In my scenario, even with a 50/50 onside kick and assuming you don't recover, you will still get the ball back with time on the clock assuming your defense holds.