Hi @matildagg21,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
It looks like the wardrobe shelf was fixed in place by screwing through the side wall into the shelf. This isn't great because it relies on the strength of the chipboard to keep the screw in place.
My suggestion is to push the shelf back up into position, drill some small 5mm holes into the side wall of the wardrobe and install 2 x Taskmaster 5mm Pin Clear Plastic Shelf Supports on either side of the shelf.
Let me know what you think and if you have further questions, don't hesitate to ask.
Jacob
