Is it a good rule of thumb to use they/them pronouns as a default until told otherwise when talking about someone else who isn't present?

So last night, I, cis 22M, was on a date with a trans woman, who we'll call H, and when we got each other's Instagrams, I noticed that she and I have a mutual friend who goes by she/her, who we'll call C. I have only met C in person once at Balboa Pride last July, and she rarely pops up on my feed, so I had forgotten her pronouns. I did not think to check her bio for two reasons. One, I was at a low battery, and two, I haven't been on a lot of dates in my life, so I was trying to follow the first date etiquette of giving H my undivided attention and not be on my phone too much. I generally referred to C by they/them pronouns in the grammatical sense of, "Hey! I know them!". This offended H, who then left the restaurant in a huff, although she explained herself and where I went wrong with her in my DMs not long after. I explained my side of using they/them as a general default rule of thumb for talking about someone who I don't know or remember their pronouns until told otherwise, and all I got back in response was "That’s not a good rule". I have been applying this rule for myself for a while, as I have a few nonbinary friends who often present very masc or femme, as well as androgynous, depending on who I'm talking to at any given moment, and I'm not trying to assume anything based on stereotypes of how anyone in any place on the gender spectrum is said to present. Keep in mind, that once I do know someone's pronouns, I do my best to follow them to the letter, and I do my best to correct people who do misgender, and if I get it wrong, I just take the L and move on with the right pronouns for the remainder of the conversation and beyond. I posted a poll about this on my Instagram story, and out of 10 votes so far, only one of them said that using they/them as default is not the way to go. Overall, am I in the wrong? Did H overreact? And if I'm in the wrong, what else could I do to avoid this in the future?