Probably just a hamster.

:) jk

You probably freaked it out. Remember the trannys computer controlled so it probably saw "Hmmm torque converter should be locking up, oh shit its not, ahhhhhhhhhhhhhhhhhhhh quick throw a CEL and go into shit home mode."

And then when you let off it went "Thank you" and put it back into normal driving mode.

I cant tell you technically what happened, but you probably just tripped something. Such as hitting 7300rpms!!! Made your poor A604 mad:(. lol

If it causes you more problems id be concerned about it, but if its smooth dont worry.