This is a bit dense with legalese, but if you search for placebo it would seem to indicate that it /is/ required that they disclose placebos ...

"(a) A sponsor who intends to conduct a clinical investigation subject to this part shall submit an "Investigational New Drug Application" (IND) including, in the following order:

...

(c ) A brief general description of the composition, manufacture, and control of any placebo used in a controlled clinical trial."

http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRS...