I've lost my voice, how long until it comes back?

[Lollyheart]

It's so frustrating, I've never lost it before.
How long does it normally take to come back?

DD2 lost hers from when she got up till about 2pm. Heartless Mother sent her to school and her friends thought it was very funny. She wrote a note to her teacher explaining I was very mean and that she couldn't answer any questions etc.
Yes I was very mean, but she'd had the day before off and by 11am was climbing the walls. Not ill at all.