Select your iPad or iPhone and then click "Apps" (it may be in a different location than shown above). This should list all apps stored in iTunes. If FM Go is listed, click its icon.
Click the "Remove" or "Install" button to remove or install FM Go on your device.
File Maker will not provide another copy. I'm guessing that iOS8 didn't install the icon for Go because of incompatibility issues. I know I had some webclip icons disappear. You can attempt a reset of your phone, erase your phone, and restore a backup prior to ios8 and this should restore Go 11. Your other choice is to upgrade to the new filemaker Go and in this case you would need File Maker 12 or newer to update your database to fmp12.
I'm not a File Maker employee, I'm just another user of filemaker, sorry to bring bad news. If you don't want to upgrade a program its best not to upgrade the operating system. Companies tried to keep some compatibility with older program, but new items in the os sometime prevent it.