By analogy, to type something incorrectly would be ""a slip of the fingers."
If you had no idea of playing off the more famous "slip of the tongue" phrase, I don't think you'd use the phrase at all. I don't think typos are thought of as "slips of the fingers" as a rule.
I think we would usually just say, "I mistyped that word" or something similar.
"My hand slipped" or "my fingers slipped" would normally refer to a lost grip on something. so that it accidentally fell.
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