Reverse image search for the blanket got me this reddit post from three years ago searching for the exact same blanket (nobody could help): https://www.reddit.com/r/HelpMeFindThis/comments/hm0668/help_me_find_another_blanket_of_this_type_its/

Searching “open weave cotton blanket” found this similar, but slightly different weave blanket on amazon: https://www.amazon.com/Linteum-Textile-Supply-Lightweight-Extra-Fluffy/dp/B08GGBHGK6/ref=sr_1_6?crid=2JU1ZPUCPEIGC

ETA: I did more searching (avoiding other tasks, lol) and found that this is called a “cellular weave” and is common in hospital blankets: https://www.amazon.com/s?k=cellular+cotton+thermal+hospital+blanket&i=garden&crid=2TPDGGE4LBCG2&sprefix=cellular+cotton+thermal+hospital+blanket%2Cgarden%2C202&ref=nb_sb_noss

This one is closer: https://www.amazon.com/BATTILO-HOME-Blankets-Breathable-Lightweight/dp/B073P7B3DY

But I can only find baby blankets for sale with the exact weave: https://www.etsy.com/listing/1042906135/premium-quality-100-cotton-cellular