It is very possible that you need to go through several “driving cycles” in order for this warning light to turn itself off. A driving cycle consists of starting the engine and then driving x (I don’t recall the exact number) miles before shutting off the engine. In other words, one 45 minute drive is unlikely to turn it off, even if the problem has been corrected.
I suggest that you go through at least 5 drive cycles before you conclude that anything is wrong. If, after 5 drive cycles, the light is still glowing, then I would suggest that you do as Remco suggested, and simply buy a new cap–preferably one from a Ford dealer’s parts dept.