photoshop.exe has disappeared from my computer

Windows 10 Pro, Surface Pro 3. I have a fully licensed (perpetual) version of PSCS6 + various plug-ins, etc.

About once every 3 months I start PS CS6 and I get some sort of notice about "Your Trial version" (is about to expire, etc.). I believe the last time this happened, Chat was still available and was quite helpful. I believe a register key was involved.. Obviously, Adobe surreptitiously from time to time changes some configuration parameter, so when PS is launched, it behaves as a trial version. I assume this is an effort to switch the user from a perpetual to a CC license. It is a cheesy and unethical tactic IMHO.

I launched PS today and there is a new wrinkle.The PS shortcut launches a sign-in to CC. The dialog has the caption "Photoshop CS6 Extended." There is a paragraph headed "Terms and conditions for trial software".This is a new wrinkle.

I checked the target for the PS shortcut. It is ""C:\Program Files\Adobe\Adobe Photoshop CS6 (64 Bit)\Photoshop.exe"" But there is no "Photoshop.exe" anywhere on my C Drive, according to a Windows Explorer search. Obviously in the 2 days since I last used PS, the executable has literally been removed from my machine. Whoever removed the executable obviously configured the machine to launch the CC dialog..

So my first question is how do I get back my original licensed executable and properly configured plug-ins, brushes, actions, etc

My second question is how do I get an assurance from Adobe that is not going to mess with the licensed executable again?

Thanks very much.