I think some Fords have little quirks sometimes. I was getting on the freeway with my 99 Ford Crown Vic & about 74 mph it started vibrating like a flat tire. As I pulled over the CEL started flashing. Got out check to see if the tires were OK. Got in the CEL was off & we drove off. That was two weeks & 2000 miles ago & it has been OK. We are on our third trip out of town all is good.
The big difference is my Crown Vic cost me $400.
But I have had other funny things happen that were just weird & only once.
It could of been anything & may never happen again. Maybe when you turned off the key it cleared. With computer vehicles I don't loose hope & call for help until I try a few times & the vehicle continues to act up.
Hope it was just a weird quirk.
1973 Galaxie 500
1995 F150 4x4
1999 Crown Vic P71