Hello everyone about a week ago I had a accident outside of work and sustained a grade 1 concussion. I went to the doctor and they told me to take it easy for a few days and advised me not to work. I got a note and sent it and my summary visit stating my injuries over to my work. I then asked my coworkers to cover the shifts I wouldn't be able to work (which I still have messages for) . I was unable to find coverage so I called in and let them know I wouldn't be able to attend. Today was my first day back and they wanted to write me up and discipline me for calling in sick. Is this legal for them to do even though I provided my documents? I live in Colorado if that matters.