My 06 had a problem maybe like what you describe. It was cruising normally down the highway and then nothing... no power to the wheels in any gear. Park worked and stopped the vehicle from rolling but everything else acted like neutral. I had no engine lights indicating a problem or anything of that nature, the vehicle was running fine.
I towed it home and ended up pulling the trans out. I replaced the Torque converter with the Euro Version unit which was around $400 or so (it came with the Torque converter bolts as well). The dealership probably cannot find this part when they search for it based on vehicle however they can find them if they search the actual part number. I cant remember the number
I also used this chance to disassemble the front pump / valve body and install a TransGo Shift kit. I replaced all filters and fluid during this ordeal as well, even though I had replaced fluid and both filters about a year before. I had to take it to a dealership to perform the quick learn operation on the trans after all the changes which was about $50. It has so far been fine since then after a few weeks of rough shifts.
It is kind of a big job pulling the trans on one of these I worked on it almost every night for a few hours for almost 2 weeks to get everything out and back in/buttoned up.
There ended up being no metal fragments or anything in the transmission, The Torque Converter piece that attaches to the Impeller/Transmission input shaft had somehow broken free of the impeller allowing it to "freewheel" inside the Torque Converter without actually sending power into the transmission.
This is the thread that I was posing in for troubleshooting and such.
viewtopic.php?f=5&t=82105TC+Bolt kit as #RL037142AA - this is what I purchased
TC only as #04736914AA
TC Bolts package as #01949765
If you end up pulling the trans pump/ the metal frisbe between the TC and Trans pump you will probably have to replace it. The gasket/material in the middle around the trans pump will come off on the trans pump when you pull it out and then will not seal when reinstalled.