https://www.rei.com/product/127507/rei-co-op-multi-towel-mini
This is my guess as to what it is. The guy is wearing a backpack for hiking/walking. He probably got other gear when he got the backpack. Hikers tend to use bandanas or small towels and tie them in this fashion for quick access. As mentioned in this thread he probably used it for his paramedic costume.
When you look at the torn fibers, it looks like those of life jackets https://rrfw.org/RGCwiki/images/thumb/5/57/IMGP2293_rip_in_cloth.JPG/300px-IMGP2293_rip_in_cloth.JPG
Pic isn't ideal but it tends to make long semi rigid strings like those on the side of the demshevik's towel
I wouldn't say it's the exact same type of material, but it seems close
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