Transmission issue with 2006 Escape
 

Hello, I have a question about a automatic transmission issue that I am having with a 2006 Ford Escape. This issue started the other day while my son was driving the Escape down the Highway. The Escape was driving normally and we have never had any issues what so ever, then it all of a sudden acted as if it had came out of gear, allowing the engine to rev., as if it was in Neutral. I had him get the vehicle off the highway and have it towed, so as not to cause any more damage, if there was any. I then had my son check the transmission fluid and it was at it's proper level, still pink and no stink. Once I was able to get to the vehicle to check it out (140 mile trip), I found that from a cold start, the vehicle shifts normally, but once the motor and transmission are warmed up to normal operating temperature it will not shift into any gear. Not only will it not shift into any gear, but you can not feel the transmission make any attempt of any type of movement. Does anyone have any ideas as to what would cause this? and, is it electrical or mechanical?