Bill, you are the one who is ignorant. You don't say "I sent you a texted message" because the "text" there is a noun not a verb. Do you make all your nouns past tense then? E.g. Bill's cat is black. Bill's catted was black. No! It's quite simple, text, texting, texted. Very simple regular English rules applied. Just like mix, mixing, mixed, you add an "ed" on the end for past tense. In olden times you would pronounce the "ed" as another syllable e.g. mix'ed, text'ed.