The Adaptive Limiter has vanished from the plug ins menu  The Adaptive Limiter is running on all of my previously saved projects and functioning but I can no longer find it for new projects.  Has anyone experienced this.  Any suggestions or has it vanished forever.

Check to make sure it is still in your VST folder.
I guess it is possible your anti virus could have contained it thinking it was malicious.
Check there if its not in the VST folder.
 
Then do a rescan of plug ins.
To answer your Q: No, I've never had this happen but those are my theory's on what could have happened.

I have checked the VST folder and it is gone and it is not in the command center either so it has vanished. Is there anyway of obtaining another copy of it or can someone recommend another similar plugin that would be equivalent or better as a replacement.    

The Adaptive Limiter is not a standalone product in Command Center.  It is installed as part of the Engineering FX Suite.
 
Try running that installer again.

The plug-in must be installed or previously saved projects would complain about the plug-in being missing. The Adaptive Limiter is VST3 only. The default path to the plug-in is "C:\Program Files\Common Files\VST3\Adaptive Limiter." It should be listed in the Plug-In Manager in the VST3 Audio effects. Using the browser select one of the "Sort By" layouts from the plug-ins tab and search for the plug-in.

Check your anti virus log

stxx
Check your anti virus log

That's my guess as well. Sometimes certain anti viruses have different sensitivity levels.
Or a reputation scan has not heard of this DLL before and S cans it.

If it were quarantined previous projects would complain about a missing plug-in.

scook
If it were quarantined previous projects would complain about a missing plug-in.

True but this is anything but logical.
 
OP Said;
""I have checked the VST folder and it is gone""
 
So how would it show up in previous projects ?

It is a VST3 plug-in. Not clear if the OP looked for VST2, VST3 or both.