How one experience made me vow never to leave a rudely worded note on someone's windscreen.

It was a freezing cold Saturday in the middle of July, when I stumbled upon an invaluable lesson.

I was attending a small film school for a weekend course, and was particularly struck by a man, probably in his early thirties, who sat across from me.

He had messy brown hair and kind brown eyes, and sat in a wheelchair.

We were all there because of a keen interest in documentary making, and part way through the day the teacher asked what story it was we were all so desperate to tell.

Mine was so inconsequential I don’t even remember it, but I will never forget his.

This man was driving home one night, in his mid twenties, and had seen a dog in the middle of the road. He exited his car, with his girlfriend in the front seat, and went to make sure the dog was alright, before ushering it off the road. As he lent down to tend to it, he was hit by a car.

LISTEN: What happens when your daughter with a disability grows up? Mia Freedman speaks to Vanessa Cranfield. Post continues below. 

I remember him saying when he regained consciousness he couldn’t really feel any pain. He was in shock. It would take some time for him to realise the full extent of his injuries.

That momentary decision, to assist a helpless animal that was in danger, cost him the ability to walk. He was no longer with the girlfriend who was sitting in the front seat, and had found the limitless opportunities that lay before him, evaporate one by one. Part way through his story, the man stopped to let out a deep and extended sigh, that said just about as much as his words did.

He was tired. He wished this hadn’t happened, but it had, and he was doing his best.

As I watched him throughout the day, I recognised, though it might be obvious, how difficult the simplest things were.

We shot B-roll on cameras, panning, and slowly walking backwards. It was a movement I didn’t think twice about, but as I glanced at him, I realised how difficult it was to move while also holding a heavy camera, that for me required both hands.

At the end of the day, I headed back to the car park with him, talking about what documentaries we loved.

We were parked near each other, and as we approached his car, we noticed a fine, accompanied by a note.

In the rush to get out of his house, to attend a weekend course he knew would not be easy, the man had forgotten his disability sticker.

The fine was for parking ‘illegally’ in a disabled spot, and the note reminded him, “Not sure if you can read, but this spot is for people with a DISABILITY.”

“I’m so sorry,” I said to him, uncomfortably.

“Oh, I can be a bit forgetful sometimes,” he mumbled. “Happens all the time.”

As I drove home, my distress at the situation turned to anger. The person who had left that note had made a bold assumption, risking the possibility that the person who’d parked there was, in fact, disabled and had accidentally forgotten to display their disability parking permit.

Stories like this one happen all the time. Just yesterday, an incident was circulating of a woman in Queensland who was shamed for using a disabled parking spot.

The note left on her car read, “Why are you parking in a disabled carpark when both you + your daughter are perfectly capable of walking???? Wrong – shame on you for using the sticker ungraciously.”

Her 13-year-old daughter, Hailee, lives with Joint Hypermobility syndrome, Glycogen Storage Disease and Muscular Dystrophy, conditions that mean she spends most days in a wheelchair.

That day, she’d been well enough to walk into the local shopping centre.

Though I’m sure there are people in the world who have parked in disabled spots without justification, there are many more who live with disabilities that are either not visible to the naked eye, or have simply forgotten the necessary permit.

Is wrongly accusing an individual of feigning disability, who may already be doing it tough, really worth the risk?

I made a simple vow to myself on that Saturday.

I’ll never be the person to leave that short, angry letter, stuck on a windscreen, to an anonymous person, who is granted no right of reply.

You simply do not know what someone is going through – and that’s a lesson we all need to be reminded of from time to time.