Yep! The "it" is implied by verbs in the definite conjugation. Thanks for introducing us to the Neoton Família!
There is no definite conjugation here. Van can't even take definite forms since it's not a transitive verb. Volt simply is the third person singular past conjugation and the subject is implied.
“He or she was not there” is correct as well, and should be accepted. I am reporting it.
Don't report it. Duolingo accepts It was not there/ He was not there /She was not there. The "he or she" variant is not needed.