I don't think you've necessarily ruined it. In my experience the screen on-off switch is particularly fussy but tends to recover easily. It might just be some dust there - easiily collected through the switch hole - trapping moisture. Then the switch can easily be fixed just by opening and cleaning the phone. Might just be the case, since I have cleaned mine once and I no longer experience similar symptoms. Coincidence? Perhaps.

BTW, in early 1980s, I left a digital watch in my trousers pocket in a plastic bag on the beach in the full sun for the whole day. The watch acted weird the whole evening and I thought it was a write-off, but it recovered by the morning