My thought: "The boss wants to see you. . . I thought I'd tell you before you saw him." is incorrect. I agree with your thinking, Bryan, that it feels odd to use past tense here, since the event has not yet occurred, BUT remember that lots of wrong usage may still be commonly used, depending on age, education level, regional variation, cultural preferences (Ex. British English/American English conventions), etc.
Almost everyone agrees that "ain't" is nonstandard and wrong and an uneducated over-extension that attempts to fill the gap in English of a first person negative ("they aren't" . . . "she isn't" . . . "I amn't"???) but people use it constantly, either naively or ironically . . .
Also, if "wrong usage" gets used for long enough, it eventually becomes an "irregular" feature of the language. English is filled with these historical blips that defy grammatical rules . . .
British English: I've got to go. (have got to)
American English: I gotta go. ([have] got to)
Message: It's good to learn the conventions and rules of English grammar but don't be too worried if there are many variations. Grammar rules are made to be broken!
