Very large metal shinning the reflection of sun triangle UFO.

I was driving north on Hwy 4 about 1 mile south of Hwy 37 intersection when I noticed that there was something shining to my northeast. I looked and there was a very large (much bigger than any plan I have ever seen) stainless steel colored triangle shaped object in the eastern sky that was reflecting the bright September setting sun in the west. I kept trying to understand what the object was... was it that Devin tower in the OKC area reflecting as I have seen that before when I am down town, but I am much too far away to even see that building from the spot I was driving. The object anyway seemed to be much closer (within 5 miles I would think) and maybe only 3-5 thousand or so feet off the ground or so. I am use to seeing paragliders in the area, but there was not sail. My family thinks it might have been a drone, but there was not propellers and it was very big. It might be a mylar balloon, but it was triangle shaped... I am baffled. I have never seen anything like this and I wonder if anyone else in this area saw. it. It lasted 30 seconds or less because I drove into where the treeline hid it and when I went to pull onto hwy 37 2 ish min. later... it was gone. I never heard anything that accompanied it.