Not a text message, but a phone call. This was back in the late 90's, so just as cars in phones were becoming more common.
My then DP was out for the day with his brother (I'll use IL references even though no-one was married because it's easier). They'd had to go a long way for some reason - can't remember why - but it was quite a big thing and they'd been out all day, driving a long distance.
My SIL (BIL's DP) did NOT get on with her in laws (my DP's parents) and they were very much low, almost no contact as a result of MIL's interfering.
[Backstory: MIL was fine with me, but BIL was her "baby boy" and SIL was a fair bit older than him so was v difficult for MIL to accept.]
They were much later back than anticipated, so MIL, worrying, called me to find out if I'd heard from them. In that call she said "Can you believe it? Julie^ called me to see if I'd heard from them!" She sounded delighted that perhaps they were starting to turn a corner and get on.
So when my DP calls me to give an update on their journey, I say "Oh - your Mum called. Guess what?? Julie called her!"
My DP "errrr.... ha ha.... John^ (BIL) is laughing at that!"
Yup - I'd forgotten that this new fangled thing called hands free had been invented and I'd just gossiped about my SIL, right in front of my BIL!
In the grand scheme of things it wasn't anything bad, thank god, but 19 year old me wanted the ground to open up and swallow me!
Still makes me cringe to this day when I think about it.
^name changed!