Capturing loop info in multiple loop & merges

I'm running a series of loop/merges where I am randomizing the order and having Qualtrics show only one loop to each respondent. If relevant, I'm looping through links to images. What's the best way to capture which loop (image) is shown to a particular respondent? i.e. which loop they got to see in each loop/merge?
Looks like Qualtrics does not record this automatically, but I'll need to know which image each respondent saw. Ideally, I want Qualtrics to populate a variable for each of the loop/merges where the content of the variable is the link the respondent saw.
My first thought was to use embedded data and piped text somehow in hidden question, but I haven't been able to figure out how to attach the embedded data within or to each loop/merge so it's capturing the right thing.
What's the best way to do this?