It is possible that the REGEQN option is not supported in the device that's used in the creation of EG output. When you go to the Tools--> Options menu, look for the Results Option in the navigation pane and click on the Graph results option. if the Graph results option for Graph Format is set to "ActiveX" or "ActiveX image", then try changing the value to GIF or JPEG and see whether you get the REGEQN to appear.
The path may be slightly different to change Graph options in 9.2. The bottom line is that if you search in support.sas.com using the search string: REGEQN ActiveX
you will see a hit on a documentation topic entitled "Summary of ActiveX and Java Support for PROC GPLOT". You will see that REGEQN is not always supported using these drivers (which is the EG default for graph creation). This is a good topic to consult when you are using SAS/GRAPH and EG because some options that work with graphic types like PNG, GIF or JPEG do not always work with ActiveX and/or Java.