I think the guy was really excited to be getting what he needed to bring his pin back to life, the same reaction many of us have.
And just because your listing says you’ll ship right away doesn’t mean that’s true, again like many of us have experienced.
So rather than assume you’re a man of your word, he jotted off a quick note that to him conveyed his appreciation and excitement. You obviously perceived it differently.
I don’t think you deserved the negative but I can see how he felt offended that you took his positivity and flipped it.