1) I pulled up a project I'd not opened for some time which had a guitar track I did with Guitar Rig 5. The track still plays with that sound, but GR5 isn't listed in the track any longer and is not in my VST list where it once was. GR5 is still on my PC and is available as a stand-alone. When I click on the GR5 icon on my desktop, it tells me that it's already running. I'm assuming that's why I'm still hearing the original sound I cut the track with - it's still pulling it from GR5.
 
2) I took the free upgrade from TH2 to TH3 a few months back & it is also only available as a stand-alone. Did I get a teaser version and have to purchase the full upgrade to have it in SONAR?
 
Thank you!

In my experience, Sonar will generate an error message if it cannot find/load a plug-in into an existing project.
 
Have you tried using the search box in the Sonar's Plug-In Browser? If nothing is found, I would try a VST reset/rescan in Preferences.

I have never heard of a missing plug-in ever affecting a track. If you are using a custom layout, try one of the full layouts like "Sort by Category. Also if the plug-in was configured as a synth, it would be in the synth list instead of the effect list.
 
SONAR includes TH3 Cakewalk, not the full version of TH3.

Thanks telecharge and scook! Will give those a shot