I know, this one is so frustrating! I was not the original observer and this is the only image taken. I really want to get an answer not only for my friend but for me; I’m so curious! I was definitely leaning beetle larva but then had to consider the caterpillar possibility too. I still think there is someone out there who knows the answer but I don’t know how else to elicit help!

Have you considered also posting to iNaturalist?

I assumed it had been already but it has not. Thank you for the suggestion! Fingers crossed…

Another place it might be worth posting is the dipterists' forum at diptera.info. There are some very unexpectedly weird-looking fly larvae out there, although most of those are aquatic. I can't totally rule out a fly from your photo, though I think it's more likely to be something else. Even if the dipterists don't recognize it they might know someone who would. I have an account on diptera.info and, only with your permission of course, could post a copy of your image there if you like (a quirky part of their policy for the forums there is that they prefer images be embedded directly in the forum post rather than a link to an outside website like BugGuide being provided). Finally, I know some folks have had luck posting images of mystery flora and fauna to taxon identification groups on Facebook; I have heard there are various such groups for mosses and liverworts, higher plants, etc. and I imagine there are some for arthropods too that you could find with a quick search.

That would be great, thank you! I have tried a couple of different facebook and reddit groups with no luck, so hopefully the Diptera forum or iNat yields some result.

Link to Diptera.info post:
https://diptera.info/forum/viewthread.php?forum_id=6&thread_id=114617&pid=473711#post_473711