[E2013] [OWA][C#][Windows version]Message class in "View source code" missing

Hello,

in OWA 2010, when I opened a message and then used "View source code" I could find this string :
 oPage.declareSubPageVariable("a_sT", "IPM.Note", VARIABLE_SCOPE_SUBPAGE); 
in OWA 2013 I am unable to find it through "View source code" (neither using IE, Chrome or Firefox).

We need it, because our application is checking if opened message is IPM.Note or IPM.Note.Something and changing it behavior based on it .

Is it possible to find this variable anywhere in OWA 2013 ? Or is there any way, how to add it there ?

Thanks in advance