I was. Due to to crossed wires admittedly, but ultimately my fault for not checking.
My youngest goes to a SEn school because of complex health needs. I had a hospital appointment at the big hospital in the nearest city in the morning and then I had booked to get my hair cut & coloured while I was in the city. I’d booked her into after school care for the day to give me time.
DD had been off school all week because of multiple appointment so I hadn’t had a single break as DH was away with work and was really looking forward to that hair cut and the chance to recharge a bit.
Sure as fate the night before I get a message saying that her class was closed the next day because the teacher and one of the TAs had covid symptoms.
BIL happened to be at mine when I got the message so was very sympathetic when I had a bit of a frustrated moan etc. then when he got home he obviously told SIL who messaged and offered to come round and mind DD for the day.
She referred to my “plans” and for reasons I still don’t understand I didn’t doubt check with her. We chatted about when I’d need to leave, the traffic and she even recommended somewhere I should go for lunch.
I missed that she was offering hospital appointment plus lunch babysitting. BIL hadn’t mentioned the hair appointment. When she recommended the lunch place I assumed (wrongly) that she was recommending it for the gap between appointment and hair.
I went, had my appointment, went for lunch - including a cringy text to SIL thanking her for the recommendation as it was fab - and then got my hair done while she sat and wondered why the fuck I hadn’t reappeared yet.
It was weirdly awkward for a couple of weeks when I got back as she was silently fuming and I didn’t realise why. Eventually BIL told me she was annoyed that I’d “disappeared” for two hours and we got to the bottom of it. We’re all good now. We do check arrangements very carefully when making them and never rely on BIL for details!