The reason why I ask is because I see that we have the linguistic means to 'point to' or 'refer' to the actions that had taken place. For example, you could say, 'what happened', and I imagine a response necessarily involves a verb. You could also say things like, 'what will you do'? and 'how did you do that'. I think that words like 'happened', 'do', and phrases like' do that' act as references for verbs in the same way that pronouns stand in for nouns. Is this formally recognised, and if so, what do we call such references?
According to Halliday and Hasan(1976:39), substitution is a kind of grammatical cohesion for clinging onto a kind of semantic relationship. In linguistics, 'pro' means 'for', an empty category. Pro-verb as opposed to proverb which professor Lawler explained in the comments is a coinage of Otto Jesperson in early twentieth century to explain what pronouns are to nouns, pro- verbs are to verbs. He even ventured to explain pro-adjective, pro-adverb or pro-infinitive.
In Grammar.about.com, Richard Nordquist while defining substitution in a light hearted moodrefers to Gelett Burgese's nonsense poem, "Purple Cow"(1985):
I never saw a purple cow,
I never hope to see one;
But I can tell you, any how
I'd rather see than be one.
ONE in this poem serves the function of nominal substitution or, simply put, is a pronoun. DO/BE/HAVE often discharge this pro-verb function (with IT/THAT). 'So' and 'Not' are often found to serve such dummy word function.
- Sunday the tenth looks pretty good, and, so does Monday the sixth.
However, as general words for any type of substitution or to avoid repetition Nordquist uses the term FILLER or ELLIPSIS SUBSTITUTION. It is better to use such general terms if there is no befitting term, say as is pronoun.