There is this thing called metadata. additional information that *can *be stored with a file. For images most of the EXIF (Exchangeable Image File Format ) standard is used. A lot of free hosters remove the exif data, because a lot of people are not aware of that info. But long story short automatic 1111 stores the prompt in the exif data. you can use the png Info tab to look at it.

other software that can show exif, can show the info as well https://linangdata.com/exif-reader/