Agreed. He overreacted big time. You didn’t just offend him. You GREATLY offended him. Then without any prodding from you (I assume) he shows you “proof” he didn’t send it. AND then he acts all offended you’d even accuse him of such a thing and walks off in a huff. When people go above and beyond to prove their innocence by showing too emotion (hoping you’ll back down) and giving you unasked for proof, they’re guilty most of the time.
OP, when you asked him if he sent you the message, what was his exact answer verbatim? If he answered you straight up with: “no it wasn’t me”. Usually innocent. But if he said something along the lines of: “what?! How could you even think I’d do something like that? Wanna see my phone? There’s no text sent from MY phone! You’re crazy!!” Then he’s lying. Notice in the second answer he never comes out out and flat out says no. Good luck OP.