Dear Mr. Walker, 
from  "Tim_Wallace@doh.state.fl.us"

Thank you for your internet feedback and question.  I apologize for the delay in this response.  I am not aware of any legal requirement for reporting a discovery of Chinese drywall in a home by a home inspection professional.  It is my understanding that this a voluntary decision for the occupant/property owner.  Here is some information you can share with the client or the property owner if they are interested.

1.  If a homeowner or occupant wishes to participate in voluntary phone based health survey, they may contact the county health department, environmental health office or my office in Tallahassee.  Should one chose to participate in the voluntary phone-based health survey the personal identifying information will be held confidential from public record release. 

Local County Health Department Contacts - Indoor Air
http://www.doh.state.fl.us/Environment/community/indoor-air/localcontacts.htm
(tip:  your local contact is Jim Padgett of the Marion County Health Department)
Florida Department of Health
Case Definition (12-18-09) for Drywall Associated Corrosion in Residences
http://www.myfloridaeh.com/community/indoor-air/casedefinition.html
Self-Assessment Guide for signs that a home may be affected by drywall Associated Corrosion
http://www.doh.state.fl.us/environment/community/indoor-air/inspections.html

2.  A homeowner or occupant  may report an incident related to a consumer product to the US Consumer Product Safety Commission (CPSC).  The US Consumer Product Safety Commission is the lead agency over the national investigation of corrosive drywall.   The CPSC has publicly requested that people with corrosive drywall problems report these cases to them voluntarily for the sole purpose of determine the scope of the problem.  I believe the person filing the report to CPSC may request that personal identifying information be withheld from public release in a Freedom of Information Act (FOIA) request.  

US CPSC
Consumer Drywall Complaint Report
https://www.cpsc.gov/cgibin/drywall.aspx
Federal Interagency Drywall Information Center
http://www.cpsc.gov/info/drywall/index.html

3.  A homeowner or occupant may report a consumer complaint to the Office of the Attorney General of Florida.  Such reports will be public records available to anyone that request the information through that office.

Office of the Attorney General of Florida
Focus: Economic crimes against Florida consumers, fraud, deceptive and unfair trade practices. 
Drywall case # L093-3-1024
http://www.myfloridalegal.com 
Phone: 1-866-966-7226 (toll-free inside Florida)
850-414-3600 (in Florida)
850-414-3990 (outside Florida)
Consumer complaint form
http://myfloridalegal.com/pages.nsf/Main/60FD9BD8FA71A5B185256CD1005EE5C5
How to Protect Yourself: Chinese Drywall
http://myfloridalegal.com/__85256CC5006DFCC3.nsf/0/1BD2BDD0C041B103852576BE00546482?Open&Highlight=0,drywall
McCollum: Con Artists Taking Advantage of Chinese Drywall Concerns
http://www.myfloridalegal.com/NewsBrie.nsf/OnlineAlerts/6032C2A6E5227D8D852575A100586E17

4. A homeowner or occupant may report a consumer complaint to Florida Department of Agriculture and Consumer Services, Division of Consumer Services. Such reports will be public records available to anyone that request the information through that office.

Florida Department of Agriculture and Consumer Services
Division of Consumer Services
Focus: Consumer complaints
http://www.800helpfla.com
Phone: 1-800-HELP-FLA (435-7352)
Instructions on how to file a consumer complaint with complaint form
http://www.800helpfla.com/complnt.html

5.  A property owner with home with corrosive drywall may report the situation to a county property appraiser so that the assessed property value can be reduced for the purposes of property tax relief.  Such reports will be public records available to anyone that request the information through that office.

Marion County Property Appraiser
Phone: (352)368-8300
http://www.pa.marion.fl.us/

Florida Department of Revenue
Property Tax Information Bulletin (PTO 10-10)
Assessment of Properties Affected by Imported or Domestic Drywall
http://dor.myflorida.com/dor/property/legislation/09/pdf/bulletin1010.pdf

So in a nutshell, I am not aware of any requirements for a business, a homeowner or an occupant to report a discovery to anyone.  Some property owners have chosen not to report to any local, state or federal agency for various reasons including but not limited to privacy concerns.  Since home inspectors are now (or is soon to be?) required to be licensed you might want to run your question by Mr. Richard Morrison at the FL Dept. of Business and Professional Regulation at 850-922-0336 or 850-922-6020.  Mr. Morrison is the Executive Director over the Home Inspectors (and mold/asbestos) licensure program. 

I hope that this reply is helpful and informative.  Should you or your clients have any additional information about indoor air quality and health, please let us know.  

Sincerely,

Tim