Oh MAN, lookit the Shifters laying the LAW down! That deserves a pause, rewind repeat, if I may say so.
Milamber...I'm actually gonna take a shot at this one...
(from dictionary.com): A sentence is: A grammatical unit that is syntactically independent and has a subject that is expressed or, as in imperative sentences, understood and a predicate that contains at least one finite verb.
In other words, a sentence, to gramatically be a sentence, needs a noun or pronoun (expressed or implied) a verb and it must be able to "stand alone".
I think "Go" could count. You is implied, go is a verb, and I believe it can stand on its own.
After thinking, I did a GIS and found this:
"Contrary to what you may have found doing an Internet search, the shortest English language sentence is not “I am.” Follow along now—it does get technical.
“I am,” first of all, is not a sentence. An English sentence must have a subject / predicate relationship, and the key element in that relationship is the type of verb that creates the predicate. Verbs either show action or they do not. Verbs without action, such as “am,” when used as a predicate, must have something to complete the meaning—a complement. So you “am” “something.” “I am happy” is a sentence since “happy” is fulfilling the complement role. Therefore, “I am” is not a sentence.
The shortest English sentence is probably “Go.” “Go” is an action verb and can be used in imperative mood, which means that it can be used with good, old “You Understood.” So “Go” actually means “You go.” On the other hand, if that interpretation doesn’t strike your fancy, let’s say that understood meanings are disallowed, then “I go” is the shortest sentence. “Go” doesn’t require a complement since it is an action verb nor does it require a direct object. With a total of three letters—the same number as the illegal “I am” contender—“I go” should reign as the champion, unless someone out there knows of a single letter verb. (No fair pulling in Old English and foreign languages.)"
I hope this helps.