I would not have went through a dumpster or even a trash-can. Those pills could have disintegrated who know. Don’t ever feel so afraid to loose your job that you do that again. Those places are hurting for help and if it is your first offense, it should be a warning.
One thing I have learned about Narcs is get them out of your possession as soon as possible. Meaning if the patient refuses it, right after you give the other meds, find someone to help you return them to the Pixis before you finish your full med pass.