I only had this happen once in 20 odd years in practice. Two little girls, one whose parent took exceptional pride in her child's hair, the other a lively little girl! You can guess whose hair got cut! Considering over that period of time many children role played "hairdressers" often and there was considerable kit available to them it never happened again. Many is a time an adult would play along too, so - maybe because they had so much play equipment they didn't go looking for the real deal and/or the adult reminded them not to use real scissors occasionally, because scissors were always accessible. We obviously got into the habit of explaining scissor safety and where and how they were to be used, but basically, the children were not closely supervised in that respect. We were in a large hall, at least 3 members of staff on, and up to 20 children.
I should think from your review what happened, and your risk assessments you will find what you do is sufficient to put it behind you.
Don'tcha just love a bit of realism😆