When you run an old installer for Exposure 4 on a Mac running OS X 10.8, it will erase everything else in the Photoshop plug-ins folder.
This only happens during installation. If you already have Exposure 4 installed then you do not need to uninstall it. Just make sure you use a recent installer next time you install Exposure 4. The number 18.104.22.1687 or larger should be on the disc label or in the installer file name. If there is no version in the name or the number is lower then throw away the installer and get the latest from our web site.
If you have already lost your plug-ins because of an old Exposure 4 installer then you will need to reinstall them all. The deleted files are not recoverable from the Trash, but you can restore them if you have a Time Machine backup. If this happened to you then please accept our humble apologies.
This bug demonstrates why it is unsafe to save installation discs and installers. You can always get the latest and greatest installers for free from our web site.