when i left a $5 note in my jeans pocket the other week i ended up finding it when i put my hands in my pocket and it came out normal size. Unless if u put it in the washing machine in no pockets it might shrink but im not gonna try that 1 to be safe haha it’d be pretty awesome tho if it did shrink. But you wouldnt be able to use it would you? if it was to shrink lol.

They were pulling your leg if they told you that would happen with normal washing and drying. Our banknotes are made of polymer and are far more durable than paper currency. They can withstand temperatures up to 120ºC (249ºF) with no significant impact and washers and dryers never get that hot. I’ve washed and dried a number of our notes over the years and they’ve emerged completely unscathed - try doing that with a greenback.
Here’s some info:
http://www.noteprinting.com/banknotes_durability.html

Australian notes are made of plastic, and are designed to last a long time. They can go through the washing machine with no problem.

However if the water is too warm or hot they may shrink. I think it is more likely they will shrink in the dryer.

The trick is that you can put them in the oven and shrink them. They are still legal tender but I think the banks pay based on the size they now are, not the face value. (by the way, this is illega).