Oh dear, sassie, if you feel old now just wait until to get to my age 70 and you are still making mistakes

I did the same thing - ONCE - and that taught me a lesson.
As soon as I downloaded PT from here and installed it, the first thing I did was to Backup Images into a file then backed up that file to a flash drive. Then I played around with the mods and can easily go back to the originals.
Your problem seems to be getting the original game back onto your computer. It seems that you have done everything right to get rid of the old files.
Did you try backing up your save game files for PT into another folder then Deleting them from the LDW folder before reinstalling Plant Tycoon? I don't know if this would help but it is worth a try.
Best of luck and I hope you get your game back soon.