Doesn't matter that the rat "trod through its feces" as thats what they do. However, it is possible that the meal was too large for the snake to digest at an adequate speed, hence it is rotting in your snakes gut. What were you keeping your snake at? If your snake is being kept too cool this will also slow down metabolism. 32 C is too cool for the warm side to be at. Your snake should be kept with a gradient of 82-90 F. Until this problem is resolved, by either digestion or (hopefully not) regurgitation, up the warm side to 95. As also mentioned above, mineral oil acts as a laxative, but it can be quite harsh on the system and only small amounts should be used. How did you attempt to "manually de-gas" your snake? That's a bit concerning to me as well. As chas*e mentioned, if your snakes condition worsens, please seak the adivce of a qualified vet. A good one in the Toronto area are the vets at High Park Animal Clinic. They are located at 3194 Dundas and can be reached at (416)763-4200
Please learn from this and use better sense in the future. Hope your snake is ok, please keep us updated!
Disclaimer: I am not a veterinarian, and the above advice is not meant to replace the advice of a qualified vet.