K.M.
As Myrna already suggested - vinegar and baking soda will take anything out of a carpet! I kid you not - I have only recently discovered the magic of using everyday household items to clean with, and I feel like a jackass for spending money on expensive cleaning stuff...
There's no magic recipe - I would just cover the area with baking soda, pour vinegar on top, and wait for the bubbling to break up the soap. Blot it up with a thick white towel, then repat the process using only vinegar. Blot it up again. If you can still feel soap in the carpet, repeat the whole process. It should work!