Thanks Rick, good to hear it is not just me!
A bug report has now been raised with Adobe.
I think I discovered how you can coax the tab name back to Search. Worked for me so maybe it will help you.
In RoboHelp 2015, click the Project tab and Project Settings button.
Then from the General tab, click the Advanced... button to the right of the language.
Then click the "Labels" tab.
Scroll the list to the [Glossary Tab] section and change the TabCaption so it reads TabCaption=&Search.
Click OK to dismiss the dialogs and recompile.
Hope this helps... Rick
Brilliant! Thanks Rick, that worked perfectly.
I did look in Properties previously, but I was looking to see if there was a 'Search' tag that had been inadvertently set to 'Glossary'. It didn't occur to me to make the change that you have suggested. Great stuff
FYI, I raised both of these issues as bug reports with Adobe and they both now appear to have been fixed in RH Update 1.