There is likely a way, but if you know its the last one you took you can just find that yourself within the macro.
Firstly, if the image was on the clipboard instead, then you can use this macro.
If it is already in the Screen Shots folder, then it is just a question of looking for the latest file. Basically just scan the folder looking for a pdf (or whatever) file with the latest modification date.
Find Latest File.kmmacros (5.5 KB)