Don't feel bad. I was legitimately sick with a head cold and called in sick for a trip (I was a line holder until the day I was furloughed) a week or two before I was getting furloughed.

Got a phone call from a Chief Pilot, who after hearing me talk goes: "Man, you sound awful. Hope you feel better." After about 10 seconds, he calls back and says he forgot to ask me for a Doctor's note.