As of now, we only have this little bit of info. Nothing more helpful. I wonder if he was dropped off and the parents just left.
I have found a very vague possibility for his father. As there were no Reynolds families living in Vernon in the 1940 census, I decided to look for people anywhere in Wisconsins in the 1940 census, that list their 1935 residence as Vernon, Wisconsin. (Unfortunately there is no 1935 state census or anything similar).
I've come across a Harold R. Reynolds, a hired-man farm labourer. He was born in approximately 1904/1903. In the 1940 census he is listed as divorced and living in Akan Town, Wisconsin. His 1935 location is given as Rural, Vernon, Wisconsin. Here he is in 1940:
https://familysearch.org/pal:/MM9.1.1/K7JJ-Y28
In 1930, Harold was still single and working as a hired man in Kickapoo, Vernon, Wisconsin for a different family:
https://familysearch.org/pal:/MM9.1.1/X93Q-QF3#
In his WWII recruitment papers, he is listed as divorced with no dependants, but if he had signed over rights to his own child, who was disabled, he may well be with dependants and quite possibly never told anyone about his son.
https://familysearch.org/pal:/MM9.1.1/KMKC-519
Harold R. Reynolds died in 1979
https://familysearch.org/pal:/MM9.1.1/V83Q-W3Y
If this was Orvus' father, he could have married shortly before Orvus' birth, and then divorced once their only son was born disabled. It's not unlikely for the time.
Unfortunately there is no record I can find of his mother, since I have no idea what her name might be or even what surname she was using in 1940 - Reynolds, her maiden name, maybe even a second married name.
There is no access to Wisconsin birth, marriage, or death records online at all. I've also searched for married Reynolds couples living anywhere in Wisconsin with a 1935 address of Vernon, Wisconsin but none fit that I could find.