One of my DCs has major problems with organisation, keeping track of things, remembering instructions etc. He was diagnosed with dyslexia aged 10. It can be hard to spot in bright children as they are good at compensating. I would recommend getting your daughter seen by an educational psychologist to see if there is something like that going on. Symptoms of dyslexia which my DS has in common with your daughter include:
1 Finding it difficult to learn to tie shoelaces.
2 Being unable to remember several instructions at once.
3 Not being able to remember where he's put things
4 Forgetting to do things at all.
My DS also used to fall over frequently when he was younger. He often tripped over his own legs! He doesn't do that any more but does often walk into things.
Whether or not your daughter has dyslexia, these are some things that have worked with my son:
1 Label everything, including goggles, so that it comes back to you.
2 Teach your daughter to put clothes etc straight into her school bag/PE bag/swimming bag as soon as they are given to her. So if she is hot during the day and takes her jumper off, she must put it into her school bag straight away. If she is given an important form, she must put it into her school bag straight away. When she goes swimming as soon as she takes her goggles off then they go back into the swim bag straight away. Once I got my son to do this things stopped going astray. Changing rooms are chaotic places and even an organised child can lose track of their things in the jumble of clothing surrounding 30 children getting changed.
3 Give comprehensive instructions to the person picking your daughter up. Eg DD should have with her her school bag, PE kit, lunchbox and coat, please check with her that she has remembered her homework.
4 Give your daughter one task at a time. Eg "Go and find your shoes then come back and I'll tell you what you need to do next." Or, if this gets a bit tedious then write a list for her:
Eg
1 Find shoes
2 Put shoes on
3 Brush hair
4 Brush teeth
5 Put coat on
Ask her to leave the list with you or in the room where you are (otherwise she'll lose the list!) but get her to come back and tick things off as she does them so she can keep track of what she has to do without you reminding her.
I have lists for all my children near the front door with what they need to bring to school each day. All they have to do is check the list before leaving the house.
If she's struggling at school she could have a list there as well? In her drawer/locker or by her peg with PE bag, school bag, homework, coat, jumper written on it so that she has to stop and check she has all those things.
Tell her teachers that you think she has a genuine problem with organisation and enlist their help and hopefully a bit of understanding.