I got deathly sick and lost my falsetto?!?!?!!?!

About a month ago, I became very sick with what the doctors think was atypical pneumonia. This lead to severe asthma and a constant barking cough. I coughed day and night for 3 weeks at least and finally went to the hospital because I was dying from asthma. They have fixed me up since then, but I couldn't sing in falsetto. I just told myself it would come back in time, but it's been a further 2 weeks and I still can't sing in falsetto! This is kind of frightening because although it sounds really f**king weird, I do love that voice and do not want to lose it permanently.
Could anyone have a guess at what's going on?