Pickup overheated then ran fine?

2003 Ford F-150 XLT 5.4 L 

A couple of days ago I noticed the radiator cap was leaking coolant so I replaced it. 

This morning (two days later) my husband drove the truck 3 miles or so and the engine overheated. After stopping at a parking lot, he waited a few minutes to drive it back home. At the return trip the needle in the gauge was fine and the truck rode well. The overheating stopped.

I checked the fan--no problem. I tested the thermostat in boiling water and it expanded and contracted properly. I suspected an air pocket, so I burped the coolant.

I didn't have time to test drive it, but at idle for 15 minutes the temp gauge was normal and there was no overheating. Heat was coming through vents in the cabin normally. 

Question: My husband says it couldn't have been an air pocket because the day after the cap was replaced he drove the truck fine. Can an air pocket still cause overheating a couple of days after replacing the cap? My thinking is that the leak in the cap caused air pockets to form and it caused an overheating situation 2 days later.  .