Med error for missing an incorrect chart check

The floor that I'm on, the night shift nurse does chart checks for my hall and three additional halls that I do not work on. This is a loooot of checks and takes me hours to do. I try to be very thorough! But the other day, an order was written for a patient on another hall to d/c a medication used for constipation... it began with a K. I personally had never heard of it before. But the order stated "D/C K...." just the name of the medication, no dosage. I didn't see this K medication on the orders, so I checked off that it was indeed D/C'd. Also, the second shift nurse had signed that she D/C'd it, Well I got a write up today for a medication error, turns out in the chart, it was written as "sps" then the dosage after. So I missed it. Simple mistake, but I can't help but feel annoyed that I was written up for this. Is this really considered a med error?

Ps... sorry if I made this difficult to understand