I think you might be right: "I ignored them and wrote my complaint in anger" does sound like it might be some unfortunate behaviour.
One of the benefits of 'virtuous' behaviour is said to be 'a lack of remorse'. So if you're felling remorse now, then maybe that behaviour wasn't virtuous.
There are some hints here about how to define 'right speech'; for example,
"Monks, a statement endowed with five factors is well-spoken, not ill-spoken. It is blameless & unfaulted by knowledgeable people. Which five?
"It is spoken at the right time. It is spoken in truth. It is spoken affectionately. It is spoken beneficially. It is spoken with a mind of good-will."
Another sutta says that what you say ought to be true, factual, beneficial ... and that, although it might be agreeable or disagreeable, in either case, you need to "have a sense of the proper time for saying them ... because the Tathagata has sympathy for living beings."
I think if you're angry it's easy to justify angry speech: "what happened is wrong, it's right to tell them, I need to tell them that so that it doesn't happen again."
Anger however is one of the things which can cloud/distort your judgement (of right and wrong).
So if or while you're feeling angry might be one of the better times to not say too much, instead think about it again later if at all. Maybe anger used to be useful, in the animal world for example: if there's some struggle for life and death, anger might make you strong and quick (maybe it helps you to over-react physically). But seeing a mosquito in the ice cream doesn't sound like that kind of emergency.