It really doesn't matter why the original coder used the wrong modifier, as long as you fix it - once you have all the documentation so you can support the correct codes.

But I'm going to take a wild guess at the scenario.
Patient seen in clinic for a consultation, which resulted in a sigmoidoscopy. The result of the scope was that the doctor knew he needed to perform surgery - TODAY.
Patient was immediately admitted for the open colectomy, and take down of splenic flexure.
CPT tells us that any/all E/M services performed outside the hospital are coded using the initial hospital visit when they result in admission. So the code used would be the 99223.
The coder, however, was thinking chronologically. Visit had the -25 to distinguish it from the scope. The coder then was thinking that the SCOPE resulted in the decision for surgery, so that's why the -57 was added to that code.
It's wrong, but like I said, I'm just guessing as to how it happened.

The important thing is to get the documentation and submit a corrected claim/appeal with correct coding.

Hope that helps.

F Tessa Bartels, CPC, CEMC