Disciplinary action

Received a disciplinary action for a med error. During work I wasn't feeling well, and another nurse took over for me. I was in the middle of a med pass, and after giving her a report I told her the med pass wasn't finished. Few hours later I get a call at home asking if I had given a scheduled dose of narc to a resident, and I replied no I hadn't gave that resident meds. Come to find out that nurse that took over for me went to a going away potluck for another nurse, and didn't finish the med pass.I was held accountable for that resident missing a scheduled dose of narc because by the time nurse started the med pass it was time for the next dose. I was told it should be first priority to give narc's first. My answer with most residents on the hall with scheduled narc's everyone can't be first. Wondering if others feel I should have received disciplinary action for this.