tl;dr While I was hiding under a bridge from a MULE, silvery BTs came out of the ground and made my vehicle disappear from on top of the bridge and I am confused af about it.
I wasn't able to find this topic already answered here. While I did see some old discussions and speculation outside of reddit (and albeit while trying to avoid spoilers), I haven't found a conclusive answer. So here's what I saw happen that I don't understand:
I was in the central region trying to infiltrate a MULE camp heading away from the Junk Dealer. I started crossing a bridge and caught a MULE's attention so I tried to backtrack and hide. I left my vehicle on the bridge but I crouched and hid beneath the bridge and was moving the camera around to try and watch the MULE and maybe sneak up on him when he turned to leave. I wasn't sure what he would do once he saw my vehicle. But while trying to watch him, suddenly I noticed these silver BTs reaching up from under the bridge right next to where I was crouching. I freaked out and moved away some, only to find they were reaching up and clawing at my vehicle. Then they went back down into the murky ground they came out of. My vehicle was simply gone. In utter disbelief I just reloaded a save so as to not lose the vehicle. What the heck happened? Is this something where MULEs can summon BTs to steal things and I haven't had this officially revealed to me yet (ie a spoiler?) Did this small group of BTs symbolize some other player online in the same location deciding to take my vehicle away? Has anyone else seen this happen or figured it out?