This mite is the larva of a terrestrial Parasitengona. Most likely a Leptus from its flask-shaped gnathosoma, although that's somewhat speculative (it's a little hard to see for sure). The terrestrial Parasitengona is very diverse and still has many undescribed species. Almost all of them are parasites as larvae. This one is probably engorged and has dropped off its host unless, of course, you removed it from a host arthropod.