I had this happen once. Subaru Outback sat at the airport for a few weeks. Drove it about 5 miles and stopped to eat then when we started again it went into limp mode. It was a Sunday in a small town and nothing was open and we were 80 miles from home. I took a chance and disconnected the battery for a few minutes and it cleared the fault and it never recurred. Of course I did some research and the most likely culprit was a bit of moisture in the fuel from condensation which triggered the computer to put it in limp mode. Since I could not get it to duplicate it is anybody's guess to what actually caused it.